A military mission to secure Syria's chemical arsenal would require a large ground force and pose huge risks, with the outcome hinging on the quality of Western intelligence, experts say.
With the Syrian regime suspected of using chemical agents against rebels, US and Western military officials are planning for a possible worst-case scenario in which an international force would move in to neutralise the lethal weapons.
Any attempt to seize control of chemical agents in Syria would depend on the intelligence gathered by foreign spy services, which have struggled at times to track the Damascus regime's stockpiles.
"The first thing is you have to know where they are... And where are the production sites and production-related sites?" said David Kay, the former UN weapons inspector who led the Iraq Study Group.
"It seems obvious but it's not easy," Kay, now a senior fellow at the Potomac Institute for Policy Studies, told AFP.
Syria is believed to have hundreds of tons of chemical agents such as sarin and VX as well as mustard gas, but the precise details of its arsenal remain unknown.
To take control of the weapons, the US or its allies would have to send in boots on the ground, including teams of technical experts, special forces units and a large contingent - likely tens of thousands - of conventional troops to seize and guard chemical sites, analysts said.
The intervention force would have to launch bombing raids to take out air defences as a preliminary step and would also likely need to target some depots that could not be seized by a ground force.
The intervention force would also need to destroy missiles, aerial bombs and artillery shells used to deliver chemical agents, which would likely require a wave of air strikes.
Part of the arsenal could be "entombed" by bombing which destroys and seal bunkers with rubble, Eisenstadt said.
The US military has a bomb, the BLU-119/B, specifically designed to incinerate chemical agents, though the Pentagon has never disclosed how it has fared in tests.
Flawed intelligence or a single mistake in an air strike could cause a disastrous release of chemical agents that would threaten the very civilians that the US and its allies hope to protect.
