If the body language between Presidents Obama and Putin is anything to go by, this summit has been a disaster. One can read too much into these things, of course, but I am told that discussions between the pair have been unusually frank.
That normally portends a fairly disastrous conclusion, but officials seem confident that the open exchange of views may have cleared the way to a peace conference in Geneva that just might be meaningful.
They insist they do sense that Putin has come to the conclusion that it is time for the violence to stop.
When all is said and done, therefore, a deal might look like this; the Americans would agree to limit their support for the rebels and accept that existing aspects of the regime - including the military and security services - would have to remain in place after a peace accord . The Russians, in return, would then, at an appropriate moment, force Assad out.