Secretary of State John Kerry says Assad definitely used chemical weapons:
“What we saw in Syria last week should shock the conscience of the world. It defies any code of morality. Let me be clear: The indiscriminate slaughter of civilians, the killing of women and children and innocent bystanders by chemical weapons is a moral obscenity. By any standard it is inexcusable, and despite the excuses and equivocations that some have manufactured, it is undeniable. The meaning of this attack goes beyond the conflict in Syria itself. That conflict has already brought so much terrible suffering. This is about the large-scale indiscriminate use of weapons that the civilized world long ago decided must never be used at all.”