The tempo of events in Syria has accelerated in recent weeks. The government forces have scored significant battlefield victories over the rebels, and this has provoked a mixture of war provocations and peace offers from the U.S. and its anti-Assad allies.
With Obama’s blessing Israel fighter jets recently attacked Syria on three occasions; in one massive air strike on a military installation in Damascus 42 Syrian soldiers were killed. Shortly thereafter Obama finally agreed to a peace conference with Russia, which had been asking for such talks for months.
Obama is entering these talks from a weakened position; the Syrian government is winning the war against the U.S.-backed rebels, and success on the ground is the trump card of any peace talks. Obama and the rebels are in no position to be demanding anything in Syria at the moment.