President Barack Obama asked Congress on Tuesday to postpone a vote on airstrikes against Syria to allow time to explore a Russian proposal to get Syria to turn over its chemical weapons to international control.

Obama made the dramatic last-minute turnaround in closed-door meetings with members of Congress and then in a prime-time address to the nation, even as he was dispatching Secretary of State John Kerry to Geneva to meet with his Russian counterpart later this week. Their goal: a binding resolution in the U.N. Security Council, where Russia had threatened to veto any move against its ally in Syria.

“Over the last few days, we’ve seen some encouraging signs, in part because of the credible threat of U.S. military action,” Obama said in a 15-minute address from the White House. “It’s too early to tell whether this offer will succeed … but this initiative has the potential to remove the threat of chemical weapons without the use of force.”

As the United States stepped back from the thorny debate over whether to strike, Syria said it was already agreeing to the Russian proposal to surrender its chemical weapons and adhere to a longstanding global arms control agreement that bans the production, stockpiling and use of such weapons. “We are ready to honor our commitments under this convention, including providing information about these weapons,” Syrian Foreign Minister Walid al Moallem said in Moscow.

Obama, as well as the leaders of France and Britain, agreed to work with Russia and China to explore the proposal that would call for the destruction of Syria’s chemical weapons. France said it would propose a resolution that would include a requirement that those responsible for an Aug. 21 alleged chemical weapons attack in a Damascus suburb be referred to the International Criminal Court for trial.

Obama worked anew to try to rally support from a skeptical nation for military action against Syria, even if that is now more to prod a deal than an imminent threat. He said that U.S. armed forces would remain on standby, ready to strike if necessary.

“America is not the world’s policeman,” he said. “Terrible things happen across the globe, and it is beyond our means to right every wrong, but when with modest effort and risk we can stop children from being gassed to death and thereby make our own children safer over the long run, I believe we should act.”

He added, “I know that after the terrible toll of Iraq and Afghanistan, the idea of any military action, no matter how limited, is not going to be popular.”

Earlier Tuesday, Obama told Democratic and Republican senators in separate closed-door meetings that they should postpone any vote on the use of force until negotiations with Russia and Syria are exhausted. He did not lay out a timetable in his conversations with lawmakers or in his address.

Senate Majority Leader Harry Reid, D-Nev., already had postponed a Wednesday vote in the Senate as an increasing number of lawmakers expressed opposition to the use-of-force proposal and support for diplomatic negotiations. But Reid said Tuesday that the U.S. should not withdraw possible military intervention — which he said led to Syria’s willingness to negotiate — especially given Syria’s “extremely low level of credibility.”

The day’s events were a sharp change from Monday, when the Obama administration had been pressing forward with an aggressive lobbying campaign to persuade lawmakers and the American people to back a proposal to use military force in Syria despite pending negotiations with Russia on its proposals.

“The diplomatic door has opened ever so slightly, and while I have doubts about this eleventh-hour offer, it would be wrong to slam the door shut without due consideration,” Sen. Robert Menendez, D-N.J., chairman of the Senate Foreign Relations Committee, said after Obama’s speech. “A negotiated solution to a crisis is always preferable and if this possibility is legitimate, I’ll give it serious thought. At the same time, the credible use of military force is necessary to keep on the table.”