Syria's chemical arsenal at a glance

Facing the threat of U.S. military action, Syria said Monday that it welcomes a Russian proposal to hand over its stockpiles of chemical weapons.

The United States has accused Syria's government of using those weapons in an August 21 attack outside Damascus, a strike Washington says killed more than 1,400 people. Syria denies the accusation and says its own troops have faced poison gas attacks by rebel forces in the civil war that began in 2011.

Here's a quick look at what Syria is believed to have and what may be involved in its elimination.

What's in Syria's arsenal?

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• International observers believe that Syria has both blister agents such as mustard gas, which inflicted horrific casualties in World War I, and the nerve gases sarin and VX, which cause convulsions, paralysis and respiratory failure.

• Syria confirmed its possession of some unconventional weapons capability in 2012 but provided no details.

• U.S. intelligence believes that Syria has about 1,000 metric tons of chemical weapons, most of it sarin and VX stored as unmixed components, U.S. Secretary of State John Kerry said Tuesday. But it also includes finished mustard gas, rockets and shells filled with sarin and "other things I can't go into here," Kerry told the House Armed Services Committee.

    What do those weapons do?

    • Mustard gas, also known as sulfur mustard, inflicts chemical burns on the skin, eyes and lungs. While mustard gas can be fatal, it also can disable victims and can cause cancer or permanent blindness. It can also remain in the environment for days or even weeks, according to the U.S. Centers for Disease Control and Prevention.

    • Sarin, which is suspected in the August 21 attack that triggered the current crisis, evaporates quickly, mixes easily with water and can contaminate food, water and clothing, according to the CDC.

    • VX is considered the most toxic nerve agent and poisons more easily through skin contact than sarin, the CDC says. It evaporates very slowly, at about the same rate as motor oil. Like sarin, it can be emitted from clothing for up to half an hour after exposure.

    How much does Syria have?

    • Before the war began in 2011, Syria had research and production facilities near Damascus, Aleppo, Homs, Latakia and Hama that turned out hundreds of tons of chemical agents a year, according to the U.S.-based James Martin Center for Nonproliferation Studies and the Nuclear Threat Initiative, which catalogs the world's arsenals of weapons of mass destruction.

    • Syria could deliver chemical agents through a variety of ammunition, such as bombs dropped from aircraft, Scud surface-to-surface missiles, artillery shells or rockets, according to Jeffrey White of the Washington Institute for Near East Policy.

    Didn't everyone ban this stuff?

    • Syria has never signed the Chemical Weapons Convention, the current international treaty against the use of poison gas. But it did sign the 1925 Geneva Protocol, which banned the use of chemical and bacteriological warfare, according to the international Organisation for the Prohibition of Chemical Weapons. That pact forbids both the first use and retaliatory use of chemical or biological weapons against other countries.

    • The organization, which monitors compliance with the Chemical Weapons Convention, says Syria has ignored several attempts to get it to sign the current treaty. Experts from the agency were part of the U.N. team that collected evidence from the site of the August 21 attack.

    How would a weapons transfer work?

    • The Russian proposal is in its infancy, and Washington immediately expressed skepticism about the idea. But when Libya renounced its chemical weapons program in 2004, it declared what it had to the Organisation for the Prohibition of Chemical Weapons; the agency sent its own inspectors to Libya to verify the declaration, and then Libya's production plants were dismantled and its stockpiles began to be destroyed.

    • Two weapons plants were torn down and a third was turned into a pharmaceutical factory before the revolution that toppled longtime Libyan strongman Moammar Gadhafi in 2011. More than half of its 24 tons of mustard gas and about 40% of its precursor chemicals had been destroyed before the revolution halted that work, which remains incomplete.

    • But the process could be far more dangerous in the middle of an armed conflict like Syria's, former U.N. and U.S. weapons inspector David Kay said. "Doing this in peacetime is difficult. Doing this in the middle of a war may be impossible," he said.

    • Moving stocks of chemical weapons is dangerous, and other countries may not be willing to take in the agents, Kay added. After the 1991 Persian Gulf War, Iraq's chemical weapons stockpiles had to be destroyed there because no company wanted to receive them: "I suspect that's what you would have to do in Syria," he said.

    • "Dissuade yourself from the idea that you're going to move these chemical weapons to someplace outside of Syria. That's probably the least safe thing to do. And where would you move them?" Kay asked.

    • And there's still the question of whether any disclosure is complete. After Gadhafi's fall, Libya's new government reported finding more mustard gas and artillery shells capable of launching it, the Organisation for the Prohibition of Chemical Weapons says.