BEIRUT - Amid opposition claims of new Syrian chemical weapons attacks, President Bashar Assad is fast approaching an important deadline for removing his stockpiles of the deadly armaments from the country. It doesn't appear that he's going to meet it.

Assad, under the terms of a September agreement that averted a threatened American military assault, was supposed to have shipped all of its toxins to the port city of Latakia by February so they could be taken out of the country and destroyed. Syria missed that deadline and promised to finish the job by April 27. Its movements of chemical weapons to Latakia, however, stalled in late March and only resumed last week with a shipment containing a small volume of chemical agents.

Syrian officials have claimed that deteriorating security conditions have made the transfers impossible. But the United States isn't buying it. "They have the ability to [ship the chemical stockpiles to Latakia]," a State Department official told Foreign Policy. "Now they need to meet their obligation ... Syria remains behind the schedule set forth by the [Organization for the Prohibition of Chemical Weapons] Executive Council, and has provided less than half of the highest priority chemical weapons materials for removal."

If Syria misses the April 27 deadline for shipping its chemical stockpiles out of the country, the June 30 deadline for the destruction of all of Assad's chemical agents will also likely go unmet. Chemical weapons expert Jean Pascal Zanders told Foreign Policy that U.S. officials had informed him it would take up to 60 days to destroy the stockpiles once they were out of the country - a period of time that would extend deep into the summer.

And Jean-Francois Seznec of the Middle East Institute said: "As long as [the chemical agents are still in the country], we're really in a delicate situation. It's a sort of vacuum where there is plenty of opportunity for new types of events to derail the process."

That would be a nightmare scenario for the United States, which has threatened to use military force against Assad if he used chemical weapons again. Eliminating those stockpiles peacefully is so high a priority for the Obama administration that some U.S. officials have argued against escalating the American effort to topple Assad for fear that such a push would persuade the Syrian strongman to hold onto his weapons even longer. According to a Wall Street Journal report from earlier this week, "the Pentagon worries the Assad regime would halt cooperation on the removal of chemical weapons" if the United States were to begin providing military training to a larger number of Syrian rebels.

White House threats notwithstanding, new chemical attacks may have already occurred. On March 29, the Syrian opposition issued a statement accusing the Assad regime of using "poison gas and highly concentrated pesticides" to kill at least three people and injure more than 25 in the town of Harasta. The Syrian American Medical Society, a network of medical professionals that operates in Syria and claims to have treated victims of the purported attack, said that their patients "suffered from hallucination, accelerated pulse, trouble breathing and, in some cases, suffocation." This week, a senior Israeli defense official told Israel Radio that Assad had used a "neutralizing chemical weapon" in the town.

A video allegedly filmed in Harasta on the day of the attack purports to show the victims of the attack receiving basic care in a makeshift medical center. Less than a week after the alleged attack on Harasta, on April 3, opposition activists accused the regime of launching another chemical weapons strike on the Damascus suburb of Jobar. A video released on an activist YouTube group called "Jobar Revo" shows an alleged victim of the attack receiving medical care.

In the run-up to the alleged Jobar incident, the regime and opposition had accused each other of planning a chemical weapons attack on the town. On March 25, Syria's representative to the United Nations sent a letter to the U.N. Security Council claiming that his government had intercepted a phone call between two "terrorists" who were planning to release toxic gas in Jobar and then blame the attack on the regime. The Syrian opposition coalition shot back that Syria's letter represented a "clear threat" by the regime to launch its own chemical attack on the town. Nine days later, according to the rebels, just such an attack took place.

If the unverified claims prove true, Syria watchers say such attacks would be par for the course for Assad. Prior to the massive Aug. 21 sarin attack in the Damascus suburbs that very nearly caused the United States to launch retaliatory missile strikes, the Syrian regime reportedly engaged in multiple chemical weapons attacks to beat back rebel advances near the capital. Journalists for the French daily Le Monde, for example, reported repeated chemical weapons attacks in Jobar as far back as April 2013.

"The men cough violently," wrote the reporters, who spent two months in the Damascus suburbs. "Their eyes burn, their pupils shrink, their vision blurs. Soon they experience difficulty breathing, sometimes in the extreme; they begin to vomit or lose consciousness."

When the United States and Russia came together last year to broker the agreement for the elimination of Assad's chemical weapons, it appeared the two powers could finally be on the brink of working in concert to resolve the Syrian crisis. But with the two countries now butting heads over Ukraine, Syria may have more latitude to hang on to its chemical arsenal for a little while longer. According to State Department spokesperson Jen Psaki, U.S. Secretary of State John Kerry and his Russian counterpart, Sergei Lavrov, discussed the effort to destroy Syrian chemical weapons stocks during a phone call Wednesday.

"The biggest tool this whole project had was that Washington and Moscow came together with the purpose of compelling Syria to give up its chemical weapons capacity," said Zanders. "That relationship is breaking down pretty fast, and it's quite clear that Bashar Assad now is in a sort of situation where he can exploit the discord between the U.S. and Russia to whatever purposes he has in mind."

David Kenner is Middle East editor at Foreign Policy magazine.