How would Syria's chemical weapons handover work?

U.N. weapons inspectors returning from Syria arrive at the headquarters of the Organisation for the Prohibition of Chemical Weapons in The Hague, The Netherlands, on Aug. 31. Marten Van Dijl / EPA

Any plan to put Syria's chemical weapon stockpiles under international control will face immense challenges — with no guarantee that President Bashar Assad will hand over his entire arsenal to inspectors, who will have to figure out how to destroy lethal toxins in the midst of a raging civil war.

But experts say the Russian-brokered proposal now being considered by the United Nations, the White House and Congress may be the world's best shot at reducing the threat of another chemical attack from Damascus or the danger of the weapons falling into the hands of extremists.

How many chemical weapons does Syria have and where are they?

The French government has estimated the arsenal at more than 1,000 tons. Assad is believed to possess sarin and its more persistent form VX, the nerve agent tabun, and blistering agents such as mustard, phosgene and hydrogen cyanide. It's believed to have large stores of “precursor chemicals” that it could use to create more of the toxic agents.

The weapons are stored in five major locations — near the cities of Latakia, Palmyra, Homs and Hama in the north and central part of the country, and at al-Safir, near the Turkish border — although they have been moved around frequently. Syria has the ability to deliver chemical warheads about 300 miles, analysts believe.

Who would be in charge of getting rid of them?

The most likely choice is the Organisation for the Prohibition of Chemical Weapons, the multinational body that oversees implementation of the Chemical Weapons Convention. Based at The Hague in the Netherlands, it was formed in 1997 and says it has verified the destruction of 80 percent of the world's declared stockpile through more than 5,000 inspections.

Only seven states have not signed or ratified the convention — including Syria. Under any deal, it would be expected to fully disclose its stockpile for the first time.

Can we be confident that Syria's declaration would be complete and accurate?

"Relatively little is known in open sources about the amount of bulk chemical agents or weaponized munitions Syria has in its possession," said Emily Chorley, a chemical weapons analyst with IHS Jane's.

"This means it will be very unlikely that the international community can oversee the removal of chemical weapons from Syria with any confidence that the entire arsenal has been handed over."

Daryl Kimball, executive director of the Arms Control Association, noted that when the U.N. oversaw the destruction of chemical agents in Iraq in the 1990s, doubts that the job was done lingered right up to the 2003 U.S. invasion on the grounds that Saddam Hussein held weapons of mass destruction.

The Chemical Weapons Convention doesn't have a provision for punishing states for non-compliance, but there's a push for a U.N. Security Council resolution that would authorize the use of force to ensure Syria is following the rules.

Syrian President Bashar Assad Marten Van Dijl / EPA

Would inspectors be in danger?

Just last month, a U.N. inspection team in Damascus came under fire while trying to verify the use of chemical weapons. OPCW inspectors would face similar dangers without the full cooperation of the Syrian government and the opposition.

"There will need to be some sort of cease-fire," said Hamish de Bretton-Gordon, a former commanding officer at the U.K.’s joint chemical, biological, radiological and nuclear regiment, who now works for the private firm SecureBio.

What is the timetable?

When Libya agreed to give up chemical weapons in 2003, it took less than a year for the OPCW to begin overseeing destruction activity, Kimball said.

The volatile Syria situation — a civil war, the threat of military attacks from the West, uncertainty about how long Assad will be in power — calls for a faster track. But the fighting would probably slow down the work; an effort to destroy sulfur mustard in Libya in early 2011 was delayed for two years because of unrest there, Chorley said.

Because the weapons are so dangerous, destruction facilities are usually built on-site, and then it can take months to get rid of even a small arsenal.

The Times of London reported that a previous plan drawn up by the Pentagon suggested that 75,000 troops would be needed on the ground to destroy up to 500 tons of chemical weapons. Given Syria's arsenal is thought to be double that, the operation could take as many as 150,000 troops to carry out.

To put that number in perspective, a Congressional Research Service Report prepared in 2009 estimated that the number of “boots on the ground” in both Afghanistan and Iraq in 2008 was 187,000.

De Bretton-Gordon said that rather than burning, degrading or burying the chemicals in Syria, it may be expedient to just move the weapons to a place where they can be dismantled in peace. Keeping them in place and trying to dismantle them in the middle of a civil war would be impractical, he said.

"It would be a big operation, it would need both the regime and the opposition to provide a cease-fire -- some arrangement of getting masses of international community troops in there would just not work," De Bretton-Gordon said. "We're talking about thousands and thousands of troops to protect this sort of thing, so it's got to be a cease-fire between the warring factions in Syria to allow, if that's what's decided, to allow movement of those chemicals to a safer area of Syria, where they can be destroyed or outside Syria."

Chorley said that Russia could be called on to assist with the destruction, but noted that Moscow, along with the U.S., has repeatedly missed deadlines for destroying their own arsenals in accordance with the convention.

"Russia's CW program has been ongoing for over 10 years and is unlikely to be completed before late 2015," she said.