So, how did we get here? Whose idea was this new possible diplomatic solution in Syria? Russia? The United States?

Obama administration officials say the proposal to put Syria's chemical weapons under international control, and to have Russia help broker a resolution, has been on the table for some time. President Obama, they say, discussed it with President Vladimir Putin as far back as the June 2012 G-20 summit in Los Cabos, Mexico. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov reportedly spoke about the concept in April of this year.

The White House maintains that despite the conversations, Russia has consistently obstructed all diplomatic efforts at the United Nations to address the Syrian chemical weapons issue and hold the Assad regime to account. The administration, ABC News' Jon Karl has reported, has even published a white paper casting Russia as obstructionists at every turn.

(Image Credit: Alastair Grant|Alexander Zemlianichenko/AP Photo)

Now, U.S. officials say it's Russia that has made an about-face, putting forth a proposal that the Obama administration says is entirely their own.

"The ball's in their court to see if they can be serious, and whether they can come up with a proposal that's serious," an administration official said.

The White House explicitly says it is not a joint proposal.

Syria Vows to Accept Russian Plan on Chemical Weapons

"This has really been a remarkable turn of events," said Andrew Kuchins, an expert on Russia and senior fellow at the Center for Strategic and International Studies. "Putin knew Obama needed an out, and Obama may have accidentally gotten one."

A breakthrough may have occurred on Friday, Sept. 6, at the G-20 summit in St. Petersburg, where Putin approached Obama and raised the issue of the Syria crisis, officials on both sides say.

The two men spoke privately without note-takers for 20 to 30 minutes. After the meeting, Obama aides said the conversation was "not acrimonious" and included talk about how they might work together on Syria in the future but came to no agreements.

Putin said at a presser after the Obama meeting: "We have agreed on some possible scenarios designed to settle this crisis peacefully," adding that Russian Foreign Minister Sergei Lavrov and U.S. Secretary of State John Kerry would be in touch.

An administration official confirmed that account, saying "Putin broached the idea that had been discussed in previous meeting about reaching an international agreement to remove chemical weapons. Obama agreed that could be an avenue for cooperation, and said that Kerry and Lavrov should follow up on the concept to shape a potential proposal."

U.S. officials note, however, that a planned announcement of a proposal was not discussed.

Fast-forward to Monday, Sept. 9.

Speaking in London, Kerry opens the door to the possibility of averting U.S. military action. "He [Assad] could turn over every bit of his weapons to the international community within the next week, without delay," Kerry said in London. "But he isn't about to."

The State Department later declared the proposal "rhetorical."

"His point was that this brutal dictator with a history of playing fast and loose with the facts cannot be trusted to turn over chemical weapons, otherwise he would have done so long ago," Kerry spokeswoman Jen Psaki said.

Obama Makes Syria Pitch on Capitol Hill

Planned or not, Kerry's comment triggered a reaction from Russia, with Foreign Minister Lavrov promptly phoning Kerry to speak about a Russian proposal. Both men, U.S. officials say, have spoken nine times in the last three weeks. A senior State Department official confirms that before Lavrov made his initial public statement about a diplomatic plan, he and Kerry spoke by phone about it and Kerry knew what Lavrov was going to propose.

In a statement on Monday morning, Lavrov called on the "Syrian leadership not only to agree on a statement of storage of chemical weapons under international control, but also its subsequent destruction."

Vitaly Churkin, Russian ambassador to the United States, later told PBS: "We are responding to what Secretary Kerry said today. The news of Mr. Kerry's statement came after the talks and were very promptly responded to by our foreign minister Sergei Lavrov, who came up with this initiative."

Churkin said Lavrov and Kerry had spoken about this idea in previous "recent" conversations. "I think there is reason to believe that this was not something which was done completely extemporaneously," he said of Kerry.

Still, the Russian proposal appeared to catch the White House off guard. At a 1:30 p.m. ET briefing with reporters Monday, deputy national security adviser Tony Blinken and press secretary Jay Carney expressed surprise.

"We literally just heard about this as you did some hours ago," Blinken said. "So we haven't had a chance to look at it yet. We haven't had a chance to talk to the Russians about it yet."

Added Carney: "Syria was, as it has been for quite some time, a subject of conversation between the two leaders and all the various counterparts who have engaged in conversation between the U.S. and the Russians over these past several weeks and months."

By evening, Obama suggested that he had discussed with Russia the very idea of international control of Syria's chemical weapons that had been floated earlier in the day. The comments have sparked intrigue about whether Kerry's earlier remarks might have been planned.

Obama: Strike 'Absolutely' on Hold if Syria Abandons Chemical Weapons

"These are conversations that I've had directly with Mr. Putin," Obama told CNN. "When I was at the G-20, we had some time to discuss this. I believe that Mr. Putin does not see the use of chemical weapons as a good thing inside of Syria or anyplace else."

Asked by PBS' Gwen Ifill whether he had any conversations with Putin about a plan to allow Syria to put its chemical weapons under international control, Obama said, "I did have those conversations. And this is a continuation of conversations I've had with President Putin for quite some time."

Kremlin spokesman Dmitri Peskov said today, per Interfax, that it's "true, the matter was discussed."

While the origin of the latest proposal is a bit murky, one thing is clear; both the United States and Russia claim some hand in achieving it. White House officials call it a "win-win" situation.

"The proposal for establishing international control over Syria's chemical weapons is not quite Russian," Lavrov said today. "It derives from exchanges we had with American colleagues and from yesterday's statement by U.S. Secretary of State John Kerry, who said that a strike could be avoided if this problem is solved."

For his part, Kerry told members of Congress this morning that he did not "misspeak" Monday when he floated the diplomatic option. He said it arose from conversations with his Russian counterpart in the past week.

"I had some conversations about this with my counterpart from Russia last week," Kerry said. "President Putin raised the issue with President Obama at St. Petersburg. President Obama directed us to try to continue to talk and see if it is possible. So it is not something that, you know, suddenly emerged, though it did publicly."

Now comes the even harder part: ironing out the fine print. If the opening round at the United Nations today is any indication, it will be a messy process.

"Ultimately, [Obama] might have to take the Russian route," Kuchins said. "Public opinion is turning against the strike and he might be in more trouble if he avoids what is being given to him."

This post has been updated.