There was then silence until Monday, when John Kerry, the US Secretary of State, gave an off-the-cuff reply in London to a question about whether Syria's President Bashar al-Assad could avoid an American attack. "Sure. He could turn over every bit of his [chemical] weapons to the international community within the next week, without delay," said Kerry with a shrug. "But he isn't about to."
Then Kerry got on a plane to fly home, and halfway across the Atlantic he got a call from the Russian foreign minister, Sergei Lavrov, saying that he was about to announce that Russia would ask Syria to put all its chemical weapons storage facilities under international control, join the Organization for the Prohibition of Chemical Weapons, and finally destroy them all.
The Syrian foreign minister happened to be in Moscow, so within an hour he declared that Assad's regime "welcomes Russia's initiative, based on the Syrian government's care about the lives of our people and security of our country". By Monday evening, Obama was saying that the Russian plan "could potentially be a significant breakthrough", and the pot was off the boil.
The whole thing, therefore, was made up on the fly. That doesn't necessarily mean that it won't work, but it is a proposal that comes without any of the usual preparation that precedes a major diplomatic initiative. The reason we don't know the details is that there aren't any. What we do know is that everybody - Obama, Putin and Assad - is clearly desperate to avoid going to war, and that gives us reason to hope.
There is a great deal of suspicion in Washington that this is merely a delaying tactic meant to stall an American attack and sap the already weak popular support in the United States for military action.
Moreover, it will be hard to send international troops in to secure Syria's chemical weapons (at least forty storage sites, plus some weapons in the hands of military units) unless there is a ceasefire in the civil war now raging all over the country.
But the American military will be pleased, because they were really unhappy about the job that Obama was giving them, and Obama himself looks like a man who has been granted a new lease on life. There will be time to try to make this work.
Gwynne Dyer is an independent journalist, whose articles are published in 45 countries