"We judge that some elements of Syria's biological warfare program might have advanced beyond the research and development stage and might be capable of limited agent production, based on the duration of its longstanding program," James Clapper, director of national intelligence, said in a written statement presented to the Senate Intelligence Committee.
Clapper offered no further details but it was the first time officials had stated publicly that America's spy agencies believed Syria had made significant strides in its biological weapons program.
"To the best of our knowledge, Syria has not successfully weaponized biological agents in an effective delivery system, but it possesses conventional weapon systems that could be modified for biological-agent delivery," he said.
Clapper also said the civil war in Syria had become a "huge magnet" for Islamist extremists, including Al-Qaeda-linked groups.
Also Read
The UN Security Council last year approved a US-Russian deal to remove and destroy Syria's chemical arsenal.
The agreement was brokered as a way to avert US missile strikes that Washington threatened after a chemical attack near Damascus, which Washington and other Western governments blamed on the regime.