Following a meeting at the U.N. Security Council, U.S. envoy Samantha Power told reporters that doubts about existing “discrepancies and omissions in Syria’s original declaration” on its chemical arsenal have yet to be cleared up.

“I want to stress that much more work still needs to be done on Syria’s chemical-weapons program,” Power told reporters. “We must ensure that the Syrian government destroys its remaining facilities for producing chemical weapons within the mandated time frames and without the repeated delays by the Assad regime that plagued earlier removal efforts.”

Power also expressed fears that the myriad rebel groups in Syria could potentially get their hands on chemical weapons, and chided President Bashar Assad’s regime for its apparently continued use of chlorine gas against insurgents.