WASHINGTON - After a passage of wild Syria diplomacy, President Barack Obama was Tuesday sizing up a political lifeline offered by the most unusual of suspects - his chilly rival Russia.
Moscow's sudden call for its ally Damascus to put its chemical arms under international supervision had immediate reverberations in tense and divided Washington.
The odds still seem long that President Bashar al-Assad will agree to a deal to neuter the chemical arsenal he may see as an insurance policy in an existential battle with rebels.
And any eventual agreement would be fraught with obstacles - not least in implementation and verification.
The White House also fears the plan may be a ruse to buy time with prowling US warships poised to loose off cruise missiles at Syrian targets.
Plus, suspicion runs high here over Russia's motives, with relations as tense as at any time since the Cold War.
But the speed with which Obama embraced the idea hinted at the depth of his political isolation - as support fast ebbs for military action in Congress, and with his credibility as a world statesman in doubt.
In television interviews Monday, Obama hailed the nascent Russian plan as a "potentially positive" development.
"It's possible, if it's real," the president told CNN.