On Monday, when he will address the U.N. General Assembly for the first time in ten years, Putin is set to propose a way out of the Syrian crisis that would run along two parallel tracks. First, he wants the U.N. to support a military intervention in Syria, one that would allow what Putin calls an “international coalition” of powers–likely including Russia, the U.S., and Iran, among others–to work together in defeating the Islamic State. Second, and perhaps even more controversially for America and its allies, Putin wants the Assad regime to play a role in this effort—and thus to remain in power at least until Syria is stable enough to handle a negotiated change of leadership.

For several weeks, and well before he set a date for his talks with Obama, Putin has been busy putting the early stages of his plan into motion. The Russian military has deployed a formidable group of tanks, warplanes and troops around Assad’s strongholds in the west of Syria, all of which will help Putin put forward his proposal on Monday as a fait accompli: With or without the approval of the U.S. or the U.N., Russia is already mounting a military intervention in Syria to prop up Assad and help him fight off the rebel factions.

Obama will now have to decide whether the U.S. is willing to go along, and if so, on what terms. The hardest prospect for Obama to stomach will likely be aiding Assad, whose forces have committed gruesome and widespread atrocities against civilians. But in the last few weeks, even some of Obama’s former aides and closest allies have come around to the notion that Assad’s forces would be essential to any resolution of the Syrian conflict.