Prospects for a quick conclusion to a U.N. investigation of a possible chemical weapons attack in Syria will depend on cooperation from the warring parties and safety for investigators — problematic conditions in the chaos of the country's civil war, an expert on weapons control told NBC News on Thursday.

Secretary-General Ban Ki-moon said Thursday that he had agreed to conduct an investigation of allegations of an attack in the northern city of Aleppo. The government and the opposition have accused each other of carrying out that attack on Tuesday.

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Ralf Trapp, a German who works on disarmament and non-proliferation issues, specializing on chemical and biological weapons, said the first job of an inspection team would be safely getting to and operating at the site. He said then -- if the Syrian parties cooperated and the inspectors felt safe — they would:

 

• Interview victims and bystanders on what they felt, smelled, saw, etc.
• Search for remnants of any weapons used. That is often difficult and unproductive, but the earlier one gets to the scene, the better.
• Take samples at the site. Pieces of weapons are rarely found, Trapp said, but the chemical agent can be uncovered in soil, plants and, if in an urban environment, bricks and building materials. Beyond the agent, inspectors will look for chemicals left behind as the agents themselves deteriorate.
• Conduct medical tests on the victims, including taking tissue samples, blood samples and, if the teams arrive quickly enough, urine samples. Samples in some cases can be analyzed on the scene, but if the inspections are delayed, there are labs in Europe and the U.S. that can find evidence in DNA and proteins.

Trapp said a big question will be how soon the UN and the Organization for the Prohibition of Chemical Weapons – of which Trapp is a former official -- can get a team into Aleppo. He said the team would have to be large and varied, with security officers and medical officers as well as inspectors.

But each day lost will influence the speed with which the investigation can be concluded, he said, because as more time elapses before biological sampling occurs, more sophisticated DNA and other toxicological testing is required. 

With optimum cooperation and conditions on the ground, an investigation led by the OPCW could be under way in days, Trapp said. A determination, including the pinpointing of the agent, could be made within days after arrival, he said -- if there is good access to interviews and environmental and biological samples. He said his former organization has equipment at the ready and could move quickly.

But if the inspection is conducted by the kind of UN group that investigated the allegations against Iraq after the 1991 Gulf War, with countries nominating experts and then gathering them, getting inspectors in could take weeks, he said. 

Considering that Aleppo is a war zone, optimum conditions are unlikely.

Trapp would not speculate on what agents were used, but he said that he has seen no reports of blistering, and without blistering, it is unlikely to have been mustard gas — although he said it’s possible that some victims might have only internal blistering.

Evidence of a nerve gas attack, for example, would be found in corpses. Victims would show certain telltale signs, like tiny pupils, saliva around the noses and eyes. There might be evidence of convulsions.

He did not dismiss the use of more common agents that are not on the proscribed list of chemical weapons. Victims said they smelled chlorine, and those felled in the attacks reported suffocating.  Chlorine, of course, is found throughout the industrial world and in large quantities can kill. Moreover, feelings of suffocation could be associated with a chlorine attack.

The chemical has a long history of use. It was the first chemical used as a weapon in World War I by German troops against French and French colonial forces. There are reports that insurgents in Iraq used chlorine in huge quantities in their attacks.

Similarly, tear gas, if used in large quantities in a confined space, can suffocate and kill.

Trapp was careful to note that even though chlorine or tear gas are not listed as prohibited weapons on the Chemical Weapons Convention, each could be considered a chemical weapon if used as a "method of warfare" rather than as being used for law enforcement or crowd control. The convention bars the use of chemicals in general as a "method of warfare." 

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If Bashar Assad is dislodged from power in Syria, as seems increasingly likely, Russia stands to be the biggest loser in both international prestige and lost arms sales, U.S. analysts tell NBC News.

 “They are scrambling to hold on to the few allies they have,” Charles  Kupchan, a senior fellow with the Council on Foreign Relations and the author of “No Man’s World,” a book about a world order unanchored by superpowers, said of the Russians. “They’re in an extremely awkward position  --  supporting a regime that is considered beyond the pale by most of the world  -- and as a consequence are selling arms and vetoing  resolutions that are needed steps to stop the killing.”

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On Thursday, Russia and China vetoed a U.N. Security Council resolution threatening  sanctions against the Assad regime. U.S. Ambassador to the U.N. Susan Rice called the actions, “dangerous and deplorable,” and argued  on the “Andrea Mitchell Report” on MSNBC that it runs against their “long-term interests.”

Indeed,  those who have meet with members of the Syrian rebel army say no nation, not even Iran, Assad’s closest ally in the region, is as reviled as Russia, which has supplied the regime with many of the armaments used to attack the rebels and shell villages.

Kupchan says that Russia doesn’t seem to care because it’s dealing with what it considers larger issues of geopolitics.  “What’s driving  Russia’s position is Moscow’s deep discomfort at what happened in Libya and (its determination) that it not again sanction civilian protection as pretext for regime change,” he said.

Former Russian President Dmitry Medvedev, who according to diplomatic officials felt personally betrayed by U.S. President Barack Obama after agreeing to U.N. resolutions permitting the use of force to protect Libyan civilians, only to see it used to overthrow their long-time ally, Moammar Gadhafi.

“Their second motivation, more explicit , is  to salvage influence. To put it mildly, their influence has waned in the Middle East and Central Asia ," added Kupchan. “So, they’re scrambling to hold on to the few allies they have.”

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William Hartung, an arms analyst for the Center for International Policy, says there may be another, more commercial reason for Russia’s support: Syria is one of Moscow’s biggest arms customers in the Middle East, and while purchases by other regional buyers  have declined , Damascus’ appetite for first Soviet and then Russian weaponry has never wavered.

“Syria is among a handful of big buyers left for Russia,” said Hartung, who notes that former customers like Saddam Hussein and Gadhafi have left the world stage. The U.S. and Europe also are making inroads with Russia’s biggest client, India, while China is manufacturing more of its own armaments. “How do you replace China, India, Iraq, Libya and now Syria?” Hartung asks.

In fact, Syrian arms purchases  from Russia have dramatically increased over the past several years, according to documentation  from the Stockholm International Peace Research Institute  (SIPRI) and interviews with arms experts.

“Most of Russian exports to Syria over the 2001-2011 period were in the past three years,” said Hartung. “The data shows $187 million (in sales) in 2009;  $294 million in 2010; and $246 million in 2011.”  Over the past decade, Russia transferred weapons worth $857 million to Syria, about 70 percent of the total weapons Syria received in that period.  Other suppliers were Belarus ($196 million), Iran ($109 million), and North Korea ($40 million).

Major weapons sent by Russia to Assad’s government, according to SIPRI, included 2,000 anti-tank missiles, including 200 Igla-SA-18 "Grouse" models, which have been fired from vehicles, helicopters and  ships against rebel fighters; 868  surface-to-air missiles; 24 MiG fighter planes with 300 air-to-air missiles; 36 trainer/combat aircraft; as well as helicopters and artillery. Those numbers do not count the small arms the Syrian military and security forces receive from Russia.

Politically, it’s a symbiotic relationship, Hartung said of the Syrian purchases. “Some of this is about cementing  relationships,  hoping the Russians will bail them out in a pinch.”

There have been conflicting reports on Russia’s willingness to continue sales.  In early July, the deputy director of a body that supervises the country's arms trade was quoted as saying, Russia  would suspend arms sales to Syria.

“While the situation in Syria is unstable, there will be no new deliveries of arms there," Vyacheslav Dzirkaln told journalists at the Farnborough Airshow in Britain, Russia's Interfax news agency reported. But no one else in the Russian government would confirm the deputy minister’s comments, leaving open the possibility that Russia will continue to resupply Assad’s military and security forces.

'Strengthening Putin's hand'
Kupchan said continuing the arms sales might benefit Russian President Vladimir Putin.

 “I do think that in the big scheme of things, the sale of arms is a drop in the bucket financially,” he said. “It matters more in domestic politics, within the decision-making process. Arms merchants and generals are weighing in. It’s not a decisive role but it helps Putin to have them in his camp.

“It’s all about strengthening Putin's hand by standing up to the West.”

But Hartung said that no matter what the end game in Syria, Russia will come out a loser. Either the client state will be in the hands of the anti-Russian rebels or remain in chaos for months, or even years.

 Still, Kupchan said, Russia may still play a positive role in ushering in the post-Assad era.

“It’s conceivable the Russians play a role in the end game,” he said. “They cannot be exceedingly pleased the way this is gone.  I can see the Russians facilitating Assad’s departure.  I just don’t see him winding up in a dacha or gated community outside Moscow.  Probably, more like somewhere in the Arab world or Africa.”

Wherever he goes, Russia’s influence in Syria is likely to go with him.

Robert Windrem is a senior investigative producer for NBC News.