I guess every group that controls territory in Syria needs to be brought to the table without preconditions, and that's a hell of a task, because, for instance, Turkey won't allow the groups it supports to let the Kurdish groups, the second-largest controllers of territory in Syria, to attend such a meeting, but until we can get that kind of agreement where everyone sits down without preconditions and talks about a way to stop the fighting countrywide and leave people running their own areas for a while so that everyone can recover, we're not going to get out of the Assad regime. At the same time, the Assad regime may need threats—I don't know—because it feels it can win now.
I wish I had a better answer for you.