From Noah Shachtman, Danger Room:  The regime of embattled Syrian dictator Bashar Assad is actively working to enlarge its arsenal of chemical weapons, U.S. officials tell Danger Room. Assad’s operatives have tried repeatedly in recent months to buy up the precursor chemicals for deadly nerve agents like sarin, even as his country plunges further and further into a civil war. The U.S. and its allies have been able to block many of these sales. But that still leaves Assad’s scientists with hundreds of metric tons of dangerous chemicals that could be turned into some of the world’s most gruesome weapons.

“Assad is weathering everything the rebels throw at him. Business is continuing as usual,” one U.S. official privy to intelligence on Syria says. “They’ve been busy little bees.”

Back in July, the Assad regime publicly warned that it might just use chemical weapons to stop “external” forces from interfering in its bloody civil war. American policy-makers became deeply concerned that Damascus just might follow through on the threats. Since the July announcement, however, the world community — including Assad’s allies — have made it clear to Damascus that unleashing weapons of mass destruction was unacceptable. The message appears to have gotten through to Assad’s cadre, at least for now. Talk of direct U.S. intervention in Syria has largely subsided.

“There was a moment we thought they were going to use it — especially back in July,” says the U.S. official, referring to Syria’s chemical arsenal. “But we took a second look at the intelligence, and it was less urgent than we thought.”

That hardly means the danger surrounding Syria’s chemical weapons program has passed. More than 500 metric tons of nerve agent precursors, stored in binary form, are kept at upward of 25 locations scattered around the country. If any one of those sites falls into the wrong hands, it could become a massively lethal event. And in the meantime, Assad is looking to add to his already substantial stockpile. . . .

Whatever the rationale, Assad is continuing his attempts to buy the building blocks of nerve agents like sarin. The CIA and the U.S. State Department, working with allies in the region, have recently prevented sales to Syria of industrial quantities of isopropanol. Popularly known as rubbing alcohol, it’s also one of the two main chemical precursors to sarin gas, one of the deadliest nerve agents in existence. The other precursor is methylphosphonyl difluoride, or DF. The Syrians were also recently blocked from acquiring the phosphorous compounds known as halides, some of which can be used to help make DF.

At a recent meeting of the Australia Group, an informal collection of international government officials dedicated the stopping the spread of weapons of mass destruction, participants “discussed the extensive tactics – including the use of front companies in third countries – [that] the Syrian government uses to obscure its efforts to obtain [regulated equipment], as well as other dual-use items, for proliferation purposes.” Bottom line: “Syria continues to be a country of proliferation concern, with active biological and chemical weapons programs.”  (graphic: Best Thinking)