The plan Brahimi is hoping to resuscitate was crafted earlier this year by his predecessor as the Syria peace envoy, former U.N. Secretary-General Kofi Annan. Annan's plan never got off the ground, and he resigned his post in frustration.
It starts with several demands on the Assad regime to de-escalate tensions and end the violence that activists say has killed more than 40,000 people since March 2011. It then requires Syria's opposition and the regime to put forward candidates for a transitional government, with each side having the right to veto nominees proposed by the other.
If anything resembling Annan's plan takes hold, it would surely mean the end of Assad's presidency. The opposition has demanded his departure and has rejected any talk of him staying in power. Yet it also would grant regime representatives the opportunity to block Sunni extremists and others in the opposition that they reject.
The United States blamed the collapse of the process last summer on Russia for vetoing a third resolution at the U.N. Security Council that would have applied world sanctions against Assad's government for failing to live by its provisions.
Russia insisted that the Americans couldn't demand Assad's departure. It also worried about opening the door to military action, even as Washington offered to include language in any U.N. resolution that would have expressly forbidden outside armed intervention.