WASHINGTON — Russia’s proposal for Syrian President Bashar al-Assad to place his chemical weapons under international supervision and then destroy them is quickly gaining steam. Assad’s government accepted the plan Tuesday morning. A few hours later, President Barack Obama, British Prime Minister David Cameron and French President Francois Hollande announced that they’d seriously explore the proposal.

It already has the backing of United Nations Secretary General Ban Ki-moon and a growing number of influential lawmakers from both parties. There’s just one problem: The plan would be nearly impossible to actually carry out.

Experts in chemical weapons disposal point to a host of challenges. Taking control of Assad’s enormous stores of the munitions would be difficult to do in the midst of a brutal civil war. Dozens of new facilities for destroying the weapons would have to be built from scratch or brought into the country from the U.S., and completing the job would potentially take a decade or more. The work would need to be done by specially trained military personnel or contractors. Guess which country has most of those troops and civilian experts? If you said the U.S., you’d be right.

“This isn’t simply burning the leaves in your backyard,” said Mike Kuhlman, the chief scientist for national security at Battelle, a company that has been involved in chemical weapons disposal work at several sites in the U.S. “It’s not something you do overnight, it’s not easy, and it’s not cheap.”

The decades-long U.S. push to eliminate its own chemical weapons stockpiles illustrates the tough road ahead if Washington and Damascus come to a deal. The Army organization responsible for destroying America’s massive quantities of munitions says the effort will take two years longer than initially planned and cost $2 billion more than its last estimate. The delay means an effort that got under way in the 1990s will continue until roughly 2023 and ultimately cost approximately $35 billion.

To be fair, the U.S. stockpiles were far larger than Assad’s. At its height, the American military possessed 30,000 metric tons of mustard gas, VX and sarin, the nerve agent Assad is alleged to have used to kill more than 1,400 civilians late last month. Assad has similar weapons, but his arsenal is thought to be significantly smaller.

On the other hand, the U.S. chemical weapons were stored at just a handful of sites. Assad’s have been disbursed across dozens of sites, many of them moveable, so locating all of the facilities would require the complete cooperation of the Assad regime. That, to put it mildly, is far from guaranteed.

Finding and securing all of Assad’s sites would be the first major challenge of implementing the Russian plan, but it would be far from the only one. The U.S. and allied personnel would then have to separate the chemical substances themselves from the warheads of his rockets, artillery shells or missiles that had been designed to carry them to their targets. The work itself would be carried out by either robots, contractors or specially trained troops, but it would still be time-consuming and dangerous.

The next step would be to physically destroy all of chemical weapons, which can be done through one of two basic options. The first involves spraying the chemicals themselves into specialized furnaces and then burning them at around 2,000 degrees Fahrenheit for one or two seconds. Nerve agents like sarin can also be rendered largely harmless by the addition of liquid sodium hydroxide, while mustard gas can be made safe with alkaline water.

Kuhlman and other experts say that either type of destruction would have to be done at individual Syrian weapons sites because it wouldn’t be safe to move the munitions to a centralized collection point inside Syria while the fighting was raging. That would mean either building a new permanent disposal facility at each Syrian compound or bringing in newly fielded mobile disposal units from the U.S. The mobile systems have not been tested in an active warzone and may not have the capacity to deal with Assad’s huge quantities of weapons.

“Do you really want to have truckloads of chemical weapons driving around Syria during the current situation?” Kuhlman asked.

A senior Defense Department chemical weapons specialist raised a different concern. The official said the biggest security challenge would be keeping the weapons safe while they were in storage waiting to be destroyed, not while they were being moved.

“Does an insurgent group attack a heavily armed convoy of chemical weapons moving from one or more sites to a disposal facility, with lots of response plans and forces on call, or does it wait until the weapons are moved and the nasty military units go away and the disposal operations start,” the official said. “The easier target is the disposal facility.”

The official said a safer option might involve moving the weapons out of Syria entirely and doing the disposal work in a safer and more secure country.

Cheryl Rofer, who supervised a team responsible for destroying chemical warfare agents at the Los Alamos National Laboratory, said none of the work could be carried out until there was a full cease-fire between Assad and the rebels fighting to unseat him. There are no indications, she noted, that either side was prepared to come to the negotiating table or wind down a civil war that has already been raging for more than two years.

“This is simply dangerous to do while people are shooting at each other,” she said.

If the U.S. and Syria came to a deal — a very, very big if — there would still be one major wrinkle. Rofer said that the only two organizations who really know how to get rid of chemical weapons are the Russia and American militaries. Given the amount of time it would take to build and then operate the disposal facilities, those specially trained troops would need to stay in Syria for years.

In a war-weary U.S., keeping that many boots on the ground for that long would be an extremely hard sell.

Yochi Dreazen is a columnist for Foreign Affairs magazine.