After Barack Obama surprised everyone and "did a Cameron", the crunch date is September 9, when Congress next meets.
Will they back military action?
Probably, but people thought the same for Westminster. There is no consensus with Republican doves and Democrat hawks, and there is also a war-weary American public.
Could Obama go ahead without Congressional support?
Difficult. While he has the authority to do so as Commander-in-Chief, the very fact he has asked Congress to debate the issue would make it virtually impossible to defy its will if it said no.
Have claims the Assad regime used Sarin strengthened the case for action?
It could, but people need proof rather than just assertion.
Could the UK Parliament reconsider its position if new evidence were produced and fresh attacks occurred in Syria?
Possible, but unlikely. George Osborne and William Hague made clear Parliament had spoken and they had no desire to revisit the issue.