Residents digging through rubble in Kafar Hamra section of Aleppo after Sunday's missile strike
The White House has been cautious about a French finding that the regime has used chemical weapons.
"We need more information" about claims of such use, spokesman Jay Carney said.
Carney said there is a need to gather more evidence to pin down when chemical weapons were used, who employed them, and what the chain of custody was: "[We must] establish a body of information that can be presented and reviewed, and upon which policy decisions can be made."
Carney had no timetable for when the review might be completed, although he said, "I can assure you that we are working very diligently as an administration with our allies and the Syrian opposition on this matter."