Responding to a report the French government had confirmed the use of sarin, press secretary Jay Carney told reporters at the White House, "I would note that the French report that you're citing [says] that more work needs to be done to establish who was responsible for the use and the ... amount that was used and ... more details about the circumstances around it."
He said as President Obama has made clear, "we need to expand the evidence we have. We need to make it reviewable. We need to have it corroborated before we make any decisions based on the clear violation that use of chemical weapons would represent by the Syrian regime."
Obama has said use of poison gas in Syria would be a "game changer," but did not say how much evidence was needed or what the consequences would be for the Syrian regime.
As for a U.N. report along the same lines, "We obviously have been pressing for the United Nations investigation team to be allowed into Syria to pursue that investigation into the possible use of chemical weapons," Carney said.
"President [Bashar] Assad ... having called for that investigation, has consistently blocked and not allowed ... the investigation and not allowed investigators in, but we continue to press for that. But we are not relying on the United Nations alone. We are aggressively pursuing other avenues to gather the evidence that is required here."
Carney said the Obama administration was "deeply concerned by the continued fighting in Qusair [Syria] and condemn the indiscriminate killing of civilians by Assad's forces and his proxies, including Hezbollah fighters."
Carney also said there are U.S. concerns about the spillover of violence into Lebanon.