WASHINGTON - At first it seemed like just another of John Kerry's musings - Syria could stop threatened US military strikes by placing its chemical weapons stockpile under international control.
But within hours, as the US top diplomat was still in the air flying back to Washington from London, what appeared to be an off-the-cuff remark caught fire, with Russia embracing it and the Syrian regime also seemingly coming on board.
Late Monday, Obama appeared to give it his blessing, saying that what was now being seen as a surprise Russian initiative could prove to be a "significant breakthrough" in changing the course of the brutal Syrian war and the thinking of the Syrian regime.
"I think what we're seeing is that a credible threat of a military strike from the United States, supported potentially by a number of other countries around the world, has given them pause and makes them consider whether or not they would make this move," Obama told NBC.
"And if they do, then this could potentially be a significant breakthrough. But we have to be sceptical because this is not how we've seen them operate over the last couple of years," the commander-in-chief said a day before he is due to address the nation.
He told Fox television that Kerry would be in touch with Moscow to see if there was an "enforceable mechanism to deal with these chemical weapons in Syria."
Political tensions are high in Washington with Congress beginning to debate a resolution calling for approval of US military strikes against the Syrian regime after a suspected August 21 gas attack on a Damascus suburb.
So, in a war-weary world, perhaps it should be of little surprise that Kerry's idea gained swift traction.
In the slow-moving world of diplomacy however, where every remark is carefully calibrated and deliberated, it's rare to see ideas spread like wildfire.
Asked early Monday in London if there was anything Syrian President Bashar al-Assad could do to avert a US military strike, Kerry replied: "Sure."
"He could turn over every single bit of his chemical weapons to the international community in the next week. Turn it over, all of it, without delay, and allow a full and total accounting for that," Kerry told reporters.
He quickly seemed to shoot down his own idea, adding: "But he isn't about to do it, and it can't be done, obviously."
Seemingly caught off-guard, State Department spokeswoman Jen Psaki issued an email saying Kerry "was making a rhetorical argument about the impossibility and unlikelihood of Assad turning over chemical weapons he has denied he used."
Reporters traveling back to Washington aboard Kerry's plane agonized about what he had meant, all the while being assured that there was "no serious proposal" to address Syria's chemical weapons stock on the table.
Except that while Kerry was still in mid-flight Russian Foreign Minister Sergei Lavrov took the ball and ran with in, calling on Damascus to "place the chemical weapons under international control and then have them destroyed."
Such a plan would help "avoid military strikes," Lavrov insisted, apparently after he had talked for 14 minutes with Kerry two hours after take-off from London.
During the call, Lavrov said he had heard Kerry's comments and Moscow would be willing to engage in the idea of an international supervision of Syria's chemical weapons stockpile.
Kerry however voiced serious skepticism saying the United States was "not going to play games," a State Department official said.
As Lavrov's offer ignited a storm of questions, it remained unclear whether this was just another misstep by the gaffe-prone secretary of state, or a carefully choreographed plant, providing Obama with a possible exit strategy.
Obama himself added to the mystery by saying he had discussed the issue with Russian President Vladimir Putin on the sidelines of a G20 summit in St Petersburg last week.
Moving fast before Kerry hit the ground again, Syrian Foreign Minister Walid al-Muallem in Moscow for talks "welcomed" the Russian initiative - even though Assad has never admitted to possessing chemical weapons.
Britain's Prime Minister David Cameron - whose parliament voted against military action in Syria - was also quick to join in, saying it would be a "big step" if Assad were to hand over its chemical weapons.
And German Chancellor Angela Merkel said it was "an interesting proposal from Russia" adding she hoped "action would follow."