Intelligence reports of the use of sarin gas by Syria's Assad regime are being scrutinized by the U.S., with the lingering memory of the Bush Assministration's lying about Iraqi weapons of mass destruction to justify an invasion. There are varying degrees of proof that Assad's regime may have used the chemical weapon in Aleppo based on physical evidence and blood samples of victims. The U.S. is consulting with with its allies and with U.N. officials who have been barred by Syria from investigating the reports.
The President had said previously that Syria's use of chemical weapons against its own people would constitute a "red line" that would prompt some form of U.S. intervention. The refugee situation for Jordan and Turkey, both U.S. allies, has grown untenable, as civilians flee the civil war in Syria. Thus far, providing resources and arms (through friendly Arab governments) has not resulted in the overthrow of Assad, but this may have been Assad's fatal mistake.