A chemical attack in Syria could only come from the government, not the opposition, say U.S. officials, despite claims from Syria's discredited regime that the rebels launched chemical weapons near Aleppo.
The United States said on Tuesday it was evaluating allegations of chemical weapons use in Syria, but dismissed charges that the opposition had used such weapons in the two-year-old conflict.
The Syrian government and rebels accused each other of launching a deadly chemical attack near the northern city of Aleppo.
"We are looking carefully at allegations of ... chemical weapons use, we are evaluating them," White House spokesman Jay Carney told reporters. "We have no evidence to substantiate the charge that the opposition has used chemical weapons," he said.
"We are deeply skeptical of a regime that has lost all credibility and we would also warn the regime against making these kinds of charges as any kind of pretext or cover for its use of chemical weapons."
Two leading U.S. lawmakers, while cautioning that reports of chemical weapons use by the Syrian government had not been confirmed, expressed concern after being briefed on the situation by Obama administration officials.
"It is serious, and it may well take some action," Democratic Senator Dianne Feinstein, who chairs the Senate Intelligence Committee, said after the closed-door afternoon briefing. She spoke in an interview with CNN.
"I think the White House needs to complete an assessment and make some statement as to what action the United States will take," she said, according to a preliminary transcript of the broadcast obtained by Reuters.