Former United Nations Secretary General Kofi Annan’s plan for an orderly transition to democratic government in Syria was widely derided as idealistic and unworkable, but it was always the best hope for avoiding massive bloodshed. Annan’s resignation on Thursday as the special UN envoy to Syria was a grim acknowledgement that his plan isn’t working. But it also sends a powerful message to the global community of the need to develop an alternative plan.

Annan’s departure should especially be a wake-up call for Russia and China, which have blocked forceful international action on Syria. It should be clear by now that unless they help pressure Syrian President Bashar Assad to broker a peaceful transition, the country is in for a long civil war that will suck in dangerous actors from across the region.

The Assad regime must be made to understand that it can’t fight its way out of a growing, multi-faceted rebellion. The regime — a relatively small group of government officials and oligarchs — may not be beyond persuasion. Having seen what happened to Libya’s Moammar Khadafy, who brazenly vowed to crush a rebellion only to be captured and dragged through the streets, Assad and his friends should eventually be open to discussing a safe route out of power. Already, rebels have killed leading members of the Syrian government and the Assad family.

Kofi Annan’s resignation shouldn’t be the end of efforts to promote a peaceful transition of power in Syria, but a lever to shift those efforts into a higher gear.