The White House is "highly skeptical" of suggestions that Syrian rebels used chemical weapons, spokesman Jay Carney said on Monday (May 6) in response to comments by a U.N. investigator that rebel forces have used the nerve agent, sarin.

"It is very important that we establish conclusively, the evidence, about chemical weapons use in Syriaand that includes who used it, and under what circumstances and where. Having said that it is also our position, and that is why that investigation must continue and why we are working both through the United Nations and others means to gather evidence. Separate from that, or related to that, is the fact that we are highly skeptical of any suggestions or accusations that the opposition used chemical weapons. We find it highly likely that chemical weapons, if they were in fact used in Syria - and there is certainly evidence that they were - that the Assad regime was responsible."