Thursday’s announcement by North Korea that it could launch a pre-emptive nuclear attack against the United States in the face of new U.N. sanctions is a predictable escalation of the isolated nation’s increasingly aggressive stance toward Washington over the past year. But experts note that Pyongyang’s recent advances in its nuclear weapons and missile programs mean that such bellicose rhetoric cannot be taken lightly.

The escalation of the North’s oratory began not long after the country’s 28-year-old leader, Kim Jong Un,  took over from his late father, Kim Jong Il, on Dec. 28, 2011. It has been accompanied by two space launches – one successful – and a third nuclear weapons test.

 It is not unusual for the North to make threats against the U.S., Japan or South Korea. And on occasion -- as in the case of the 2010 artillery barrage of Yeonpyeong Island and an earlier attack on a South Korean gunboat -- it has carried out these threats.  It has never taken any military action after threatening the United States, however.

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Some analysts have suggested that the latest round of threats is intended to show that the young Kim will continue his father’s legacy of hostility toward the U.S.

To what end?

North Korea has long wanted the U.S. to sit down with its negotiators to hammer out an agreement to end the Korean War, which ended in 1953 not in a peace treaty but in a truce.

The North would like to gain concessions from the U.S. in such a negotiation, but its escalating threats and rhetoric have the opposite effect:  The Obama administration, like preceding administrations, has steadfastly refused to negotiate with Pyongyang.

The problem is that North Korea, which has long taken a backseat in U.S. councils to the Middle East, does have military capabilities that could at the very least threaten U.S. interests in North Asia.

According to a recent analysis, North Korea has a weapon stockpile that could threaten both Japan and South Korea and, in longer term, the United States. Some of the weapons have already been deployed, say U.S. officials, who spoke to NBC News on condition of anonymity. Moreover, the North has begun research into more advanced and dangerous weapons, possibly even thermonuclear weapons, they say. 

At the high end of the stockpile range, U.S. officials and other researchers said North Korea may already have up to "a few dozen" nuclear weapons that could be fitted atop its vast fleet of ballistic missiles. Those missiles are limited to an intermediate range, capable of hitting targets in Japan, South Korea or elsewhere in the northern Pacific, including U.S. military bases as far south as Guam, the officials believe.

Related story: UN passes sanctions despite North Korea threat of 'pre-emptive nuclear attack'

The U.S. believes the space launch tests are part of a development plan for an intercontinental ballistic missile (ICBM) capable of reaching the continental United States with a payload of several hundred kilotons — 10 to 20 times the size of the bombs that destroyed the Hiroshima and Nagasaki.

U.S. officials publicly express confidence that the national missile defense system based in Alaska would be able to shoot down any incoming North Korean ICBM.

“I can tell you that the United States is fully capable of defending against any North Korean ballistic missile attack,” White House spokesman Jay Carney said Thursday in response to a question about the North Korean threat.

 He also said the U.N. sanctions will make it harder for Pyongyang to continue to make progress on its weapons and missiles. 

“North Korea … will now face new barriers to developing its banned nuclear and ballistic missile programs,” he said. “Resolution 2094 increases North Korea's isolation and demonstrates to North Korea's leaders the increasing costs they pay for defying the international community.” 

For the past several years, the U.S. also has been monitoring North Korean research into thermonuclear weapons — hydrogen bombs and bombs known as boosted-fission weapons, in which plutonium and uranium are combined for a higher energy yield. (The problem is that if the North conducted a test and claimed that it was thermonuclear, the U.S. would have difficulty determining if the North was telling the truth. The test site at Kilchu is far enough inland that the U.S. would not have access to the particulate matter needed to make an accurate determination, experts say. )

David Albright, president of the Institute for Science and International Security, or ISIS, a nonpartisan nuclear arms research group, said last year that any tests in the future may also be about ensuring the reliability of North Korea's current weapons design.

"Once you get beyond a dozen, it makes sense to test type and reliability of your weapons," he said. Albright said then that his group's estimate of North Korea's weapons stockpile is a bit less than those provided by the U.S. officials, but that ISIS, too, believes Pyongyang has "missile-deliverable weapons."

The design of the weapons is believed to be based on Chinese models (as were the first generation Pakistani nuclear weapons). The design is basic, and was developed in the 1960s with help from the Soviet Union, which used it to produce a whole line of nuclear warheads.

While some analysts suggested that the North planned its December rocket launch to gain attention ahead of the presidential election in South Korea , some in the U.S. non-proliferation community think otherwise. They expect that once the North feels comfortable with its ICBM technology, it will deploy the missiles.  They point to the Musudan intermediate range missile which was tested in middle of the last decade, then deployed — presumably with nuclear warheads — and aimed at Japan.

Once the North has confidence in the long-range missile based on the space rocket, U.S. officials believe they will deploy it as well, making North Korea the third nation to have nuclear weapons targeted at the United States, after Russia and China.

Many in the Obama administration see that as a more frightening prospect than Iran gaining nuclear weapons, believing that Tehran is a rational actor that will serve its own national interest and preserve the regime, compared to successive generations of North Korean leaders who have shown that they are unpredictable and erratic.

But would it force the U.S. to conduct face-to-face talks with the North? State Department spokeswoman Victoria Nuland said in December that the North has a better option.

Referring to Kim Jong Un, Nuland said: "He can plot a way forward that ends the isolation, that brings relief and a different way of life and progress to his people, or he can further isolate them with steps like this. He can spend his time and his money shooting off missiles, or he can feed his people, but he can't have both."

NBC News' Shawna Thomas contributed to this report; this piece is an updated version of a post originally published on Dec. 13, 2012.

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North Korea does not appear to be making preparations for a nuclear weapons test following Tuesday’s test of a space launch vehicle, which was believed to be cover for a long-range missile test, U.S. intelligence analysts told NBC News.

South Korean and Japanese officials had feared that a nuclear weapons test — its third after previous detonations in in October 2006 and May 2009 — would quickly follow the launch.

But word that the North isn’t thought to be preparing for a test is providing little solace for Seoul or Tokyo, mainly because recent intelligence suggests that the North has made significant advances in its nuclear weapons program.

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According to a recent analysis, North Korea has a weapon stockpile that could threaten both countries and, in longer term, the United States. Some of the weapons have already been deployed, say U.S. officials, speaking on condition of anonymity. Moreover, the North has begun research into more advanced and dangerous weapons, possibly even thermonuclear weapons, they say.  

 

At the high end of the stockpile range, U.S. officials and other researchers said North Korea may already have up to "a few dozen" nuclear weapons that could be fitted atop its vast fleet of ballistic missiles. Those missiles are limited to an intermediate range, capable of hitting targets in Japan, South Korea or elsewhere in the northern Pacific, including U.S. military bases as far south as Guam, the officials believe.

'Highly provocative'
The U.S. believes the space launch test is part of a development plan for an intercontinental ballistic missile (ICBM) capable of reaching the continental United States with a payload of several hundred kilotons — 10 to 20 times the size of the bombs that destroyed the Hiroshima and Nagasaki.

State Department spokesperson Victoria Nuland hinted about that Wednesday, calling the launch "highly provocative" and a "threat" to regional security. The U.S. is "concerned that all of this launching is about a weapons program and is not about peaceful uses of space," she added.

More North Korea coverage from NBC News

For the past several years, the U.S. also has been monitoring North Korean research into thermonuclear weapons — hydrogen bombs and bombs known as boosted fission weapons, in which plutonium and uranium are combined for a higher energy yield. (The problem is that if the North conducted a test and claimed that it was thermonuclear, the U.S. would have difficulty determining if the North was telling the truth. The test site at Kilchu is far enough inland that the U.S. would not have access to the particulate matter needed to make an accurate determination, experts say. )

David Albright, president of the Institute for Science and International Security, or ISIS, a nonpartisan nuclear arms research group, said earlier this year that any tests in the future may also be about ensuring the reliability of North Korea's current weapons design.

"Once you get beyond a dozen, it makes sense to test type and reliability of your weapons," he said. Albright said then that his group's estimate of North Korea's weapons stockpile is a bit less than those provided by the U.S. officials, but that ISIS, too, believes Pyongyang has "missile-deliverable weapons."

The design of the weapons is believed to be based on Chinese models (as were the first generation Pakistani nuclear weapons). The design is basic, and was developed in the 1960s with help from the Soviet Union, which used it to produce a whole line of nuclear warheads.

ANALYSIS: 'Spoiled child' North Korea snubs key ally China with rocket test

While some analysts suggest that the North is using its space rocket launch to gain attention ahead of next week’s presidential election in South Korea -- and possibly to force talks with the U.S. — some in the U.S. non-proliferation community think otherwise. They expect that once the North feels comfortable with its ICBM technology, it will deploy the missiles.  They point to the Musudan intermediate range missile which was tested in middle of the last decade, then deployed — presumably with nuclear warheads — and aimed at Japan. 

Once the North has confidence in the long-range missile based on the space rocket, U.S. officials believe they will deploy it as well, making North Korea the third nation to have nuclear weapons targeted at the United States, after Russia and China.

Many in the Obama administration see that as a more frightening prospect than Iran gaining nuclear weapons, believing that Tehran is a rational actor that will serve its own national interest and preserve the regime, compared to successive generations of North Korean leaders who have shown that they are unpredictable and erratic.

But would it force the U.S. turn to conduct face-to-face talks with the North? Nuland said Wednesday that the North has a better option.

Speaking of the North’s 27-year-old leader Kim Jong Un, Nuland said: "He can plot a way forward that ends the isolation, that brings relief and a different way of life and progress to his people, or he can further isolate them with steps like this. He can spend his time and his money shooting off missiles, or he can feed his people, but he can't have both."

Robert Windrem is a senior investigative producer for NBC News.

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With tensions between Israel and Iran running sky high over the latter's nuclear program, U.S. officials and military analysts are growing increasingly concerned that Israel will launch a multi-phase air and missile attack that could trigger waves of retaliatory missile strikes from Tehran.

Such a shootout could quickly spiral into a regional conflict that would potentially force the U.S. to intervene to protect its interests.

The emerging consensus among current and former U.S. officials and other experts interviewed by NBC News is that that an Israeli attack would be a multi-faceted assault on key Iranian nuclear installations, involving strikes by both warplanes and missiles. It could also include targeted attacks by Israeli special operations forces and possibly even the use of massive explosives-laden drones, they say.

The Iranian response to such an attack is uncertain, but many experts and officials believe it is likely to include retaliatory missile strikes. Iran has more missiles in its arsenal than Israel, according to some estimates, and has the capability of striking targets in most Israeli population centers.

"I think that it would strike Iran as a reasonable response, an eye for an eye," said Christopher J Ferrero, a professor of diplomacy at Seton Hall University in New Jersey and an expert on Middle East missile forces.

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He also said Iran would likely attack major cities with its Shahab 3 missiles, which he said are not as accurate as the Israeli missiles, but would be an effective "instrument of terror … that could certainly cause significant damage to heavily populated suburban and urban areas.

 

 

Israel possesses advanced anti-missile defenses, but those systems could be overwhelmed if Tehran launched large numbers of missiles, as Ferrero expects.

Given the immense difficulties in carrying out successful air strikes on the four key Iranian installations using its warplanes alone -- as laid out last week by the New York Times, U.S. officials say Israel would be likely to coordinate such airstrikes with waves of missiles. This would greatly increase the chances of penetrating fortifications that Iran has built to protect some of its key installations and overwhelm Iran's air defenses, said the former and current U.S. officials, who spoke on condition of anonymity.

"Two words:  Jericho missiles," said one former White House and Pentagon official, speaking on condition of anonymity, when asked how Israel would attack Iranian targets at great distances. "They are conventionally armed, have a very small CEP (circular error of probability, meaning they are highly accurate) and can be used in conjunction with a strike fighter operation."

Israel has as many as 100 Jericho ballistic missiles – both short- and medium-range – as well as submarine-launched cruise missiles, though the officials say they believe the latter are unlikely to be used. The short-range Jericho I missiles would be of no use in an attack on Iran, because the targets are far beyond its 300-mile range. However, the  medium-range Jericho II's are capable of  hitting targets as far as 900 miles away – or as far east as Tehran. Israel also tested a Jericho III intercontinental ballistic missile in 2008 and Israeli media have reported that it may have deployed one or more of the weapons, which would put all of Iran within reach.

The missiles would most likely be launched from the Hirbat Zekharyah missile range, midway between Israel and the Mediterranean Coast, according to "Critical Mass: the Dangerous Race for Superweapons in a Fragmenting World," by William E. Burrows and Robert Windrem, and various Israeli press reports.

Although designed to be part of Israel's nuclear deterrent force, the Jerichos can be equipped with high explosives as well as nuclear warheads. U.S. officials have said that an Israeli attack, if it happens, would be intended to surgically take out the nuclear facilities, not inflict the mass casualties that would result from a nuclear attack.

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Iran has no capability to defend against a missile strike, said Ferrero, the expert on Middle East missile arsenals.

"If the Jerichos are accurate enough to get to their targets, they will get to their targets," he said.

What Iran does have is hundreds of Shahab 3 medium range ballistic missiles, according to U.S. estimates. The Shahab 3 also has a range of roughly 900 miles.

Israel, possibly supplemented by U.S. shipborne anti-missile systems – the Aegis Standard Missile-2 -- could intercept and destroy some of the incoming Iranian missiles, said Ferrero. But the numbers favor Iran, he said.

"I believe that (the Iranians) have a sufficient inventory that they could overwhelm those missile defenses and still get enough missiles through to cause damage," he said.

The critical factor may be the number of  missile launchers in Iran's inventory, Ferrero said, because penetrating Israel's defenses would require numerous  missiles, but also enough launchers to be able to fire them off simultaneously. That number is a closely guarded secret, he said.

Additionally, U.S. intelligence estimates say Iran has supplied Hezbollah with more than 40,000 short-range rockets and missiles since 2006. However, U.S. officials are uncertain whether Hezbollah would follow Iranian orders, and risk Israeli retaliation or, if they did, how many they would fire.  The majority of the rockets and missiles are unguided.  Israel and the U.S. have worked on a short-range missile defense system called Iron Dome, but there are concerns that waves of attacks could overwhelm the system.

Also open to question in U.S. and Israeli military circles is whether an Israeli attack would meet its objective: setting back the Iranian nuclear program anywhere from two to five years.

U.S. officials say Israel would be likely to concentrate its attacks on four key Iranian nuclear complexes. Key facilities within those complexes – the Natanz and Fordo centrifuge facilities, both south of Tehran; the Arak research reactor, southwest of Tehran; and a uranium hexafloride production and research facility near the city of Isfahan – are protected by heavy fortifications, they said.

The Jerichos are stored in tunnels in limestone formations around Hirbat Zekharyah and rolled out for firing. They would likely be used as part of a one-two punch, the officials say. The first attack would be carried out by Israeli strike fighters and would be intended to breach the heavily fortified outer ceilings of the facilities. The second (and possibly even third) wave would be missile attacks aimed at destroying the facilities within, the officials said. 

Asked if Jerichos would have the accuracy and the explosive power to take out hardened bunkers or fortifications believed to be protecting Iran's most-sensitive underground nuclear facilities, a current U.S. official replied, "You would be surprised at their accuracy." The official added that the missiles' warheads would contain a special mix of explosives that could penetrate the Iranian defenses.

U.S. officials also say Israel may have learned the location of facilities that fabricate centrifuge components. These, too, could be targeted.

A 2010 book on the possibility of an Israeli attack laid out the difficulties Israel would face if it attempted to use only its strike fighters on those targets.

 "Attacks against the sites at Natanz, Isfahan and Arak alone would stretch Israel's capability and planners might be reluctant to enlarge the raid further," wrote authors Steven Simon and Dana H. Allin, in "The Sixth Crisis – Iran, Israel and the Rumors of War." Simon, then a fellow at the Council on Foreign Relations, now heads the Middle East Desk at the National Security Council.

The biggest problem is the fortification of the two centrifuge facilities. Simon and Allin describe the challenge using aircraft only.

"Natanz is the only one of the … likely targets that is largely underground, sheltered by up to 23 meters (75 feet) of soil and concrete," they wrote. "… Bombs used in a ‘burrowing' mode, however, could penetrate deeply enough to fragment the inner surface of the ceiling structures above the highly fragile centrifuge arrays and even precipitate the collapse of the entire structure."

But for the attack to have high odds of success, they argue, aircraft would have to drop additional bombs into the cavities created by the first bombs. That would require "time on target" -- a luxury that the Israeli jets at the outermost limits of their 1,100-mile range would likely not have. While they estimate the success rate of such a plan at "better than 70 percent," they call it "complicated and highly risky."

Another difficulty for attacking Israeli aircraft would be finding a route to the targets that could be flown covertly or with the tacit approval of Sunni Arab states, who are at least as frightened of an Iranian nuclear capability as the Israelis.

Simon and Allin (and others) have written that there are three "plausible routes" that Israeli warplanes would take to attack Iran: a northern approach, likely along the Syrian-Turkish border; a central path that would take them over Jordan and Iraq; and a southern route that would transit the lower end of Jordan, Saudi Arabia and Kuwait. The southern route is the most likely, U.S. officials suggest, because the Saudis and other Sunni-dominated Gulf states are eager for someone to take out the Iranian threat. They prefer the U.S. do it, but have reportedly shared intelligence on the Iranian program with the Israelis, if only on a limited basis, according to the U.S. officials.

No matter what route the fighter bombers take, they would use what one U.S. official described as "high-low, low-high" flight paths – flying high first to increase fuel efficiency, then low for most of the trip to evade radar, then climbing high again as the bombs are released in what is known as a "flip toss" from as far as 10 miles from the target.

The Israelis would be prepared to lose aircraft if necessary, the officials said.

Although Simon and Allin do not discuss adding a missile component, other experts, including many current and former U.S. officials, believe the Israelis already have made a decision to have them in the attack menu.

Missile attacks would be coordinated with fighter-bomber attacks (presumably, the Israelis' F-16, F-18 and extended-range F-15I Strike Eagle). The missiles would have to be launched so that warheads strike targets following the strike fighter attacks.  Because of the short flight time, minutes rather than hours in the case of the aircraft, the missile launch would almost certainly take place at the last possible moment to ensure the secrecy of the overall attack.

The Israelis are not planning to use their submarine-launched cruise missile force -- "not enough of them," one official said of the subs. (The Israelis have long had nuclear tipped sub-launched cruise missiles as part of their deterrent force.) 

Beyond the strike fighters and the missile force, U.S. officials suggest the Israelis could use two other "weapons" against Iran.

The first is special operations forces that would be secretly inserted into the country. At the least, they could be employed to illuminate aim points for laser-guided bunker-busting bombs. At the most, they could launch their own attacks on facilities, particularly those believed to contain enriched uranium.

The other is a new generation of large drones with wingspans approaching those of a Boeing 777  (almost 200 feet). Costing $30 million each, the Heron drones are capable of remaining airborne for 40 hours at a time and have a range of 4,600 miles. While they can be equipped with surveillance and electronic warfare equipment, some officials call them "strike drones," meaning they could be loaded with explosives and used to attack Iranian targets.

While the initial days of an Israeli-Iranian conflict would probably be bloody, most experts say that the open warfare would be expected to wind down within days or weeks, since neither side has the ability to occupy the other's territory or enough missiles to sustain attacks.

But that would bring with it its own set of problems, as the conflict would be likely to continue on a lower level, involving covert operations and terrorism.

"You could have a very nasty covert war emerge," said Ferrero.

Robert Windrem is a senior investigative producer for NBC News.