Secretary of State John Kerry has said links between a poison gas attack on Syrian civilians and the Assad government are "undeniable," but U.S. intelligence officials are not so certain.
Congressional leaders and national security committees get briefed on the situation today.
President Barack Obama is vowing that American retaliation for the Syrian government's alleged use of chemical weapons on its own people would send a "strong signal."
But British Prime Minister David Cameron is promising to hold off on any action until a U.N. inspection team can complete its investigation in Syria. The U.N. says the team should wrap up its inspection tomorrow and report its findings Saturday.