Syria regime used chemical weapons against rebels, US officials say

The assessment, based on CIA tests on blood, urine and hair samples from dead or wounded rebel fighters, is the first time Washington has supported claims previously made by British and French intelligence services in recent weeks. Assad has repeatedly denied using any chemical weapons in the bitter civil war.

"Following a deliberative review, our intelligence community assesses that the Assad regime has used chemical weapons, including the nerve agent sarin, on a small scale against the opposition multiple times in the last year," said a White House statement .

"Our intelligence community has high confidence in that assessment given multiple, independent streams of information. The intelligence community estimates that 100 to 150 people have died from detected chemical weapons attacks in Syria to date; however, casualty data is likely incomplete. "

The White House believes its assessment means Syria has crossed the so-called "red line" that President Barack Obama established early in the conflict as a test for further western intervention to support the rebels. The New York Times said White House officials had detailed the aid as including small arms, ammunition and possibly anti-tank weapons, but sending the anti-aircraft munitions hotly sought by the rebels was not under consideration.

The deputy national security adviser, Ben Rhodes, said: "The president has made a decision about providing more support for the opposition and will be providing further support to the SMC (Supreme Military Council) and that includes providing military support. I can't detail what types of support yet."

He added: "We have not made any decision about a no-fly zone ... The best thing we can do is help the opposition on the ground."

Senator John McCain, a leading US hawk who has been pushing for intervention, said: "I applaud the president's decision and I appreciate it."

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