The United States and Russia agreed Saturday on a plan to bring Syrian chemical weapons under international control, a rare diplomatic victory in a brutal civil war that appears to head off a punitive U.S. military strike on Syria in the near future.

In announcing the deal, Secretary of State John F. Kerry and his Russian counterpart, Sergei Lavrov, said the agreement would be backed by a U.N. Security Council resolution that could allow for sanctions or other consequences if Syria fails to comply.

Kerry said the first international inspection of Syria’s chemical weapons stockpile is set for November, with destruction to begin next year. But Lavrov added a more cautious note to what was an otherwise jubilant moment in Geneva, where the talks took place.

Lavrov stressed that the documents released Saturday, outlining the transfer of Syria’s large chemical weapons arsenal and its destruction, constitute only an “agreed proposal” that does not yet have the force of law. The plan drew sharp anger from Syria’s U.S.-backed rebels and received decidedly mixed reviews from the U.S. Congress, across party lines.

“Providing this effort is fully implemented, it can end the threat these weapons pose not only to the Syrian people, but also to their neighbors, to the region,” Kerry said.

The agreement, if successfully implemented, marks a modest victory for the Obama administration in its mostly arms-length engagement with Syria’s 2½-year-old conflict.

It was President Obama’s threat of U.S. military strikes after Syria’s Aug. 21 alleged use of chemical weapons — killing an estimated 1,400 people, hundreds of them children — that began the process culminating Saturday in an agreement for Syria to give up its chemical stockpile.

Over the years, that arsenal has provided Syria with a strategic benefit against Israel, with whom it is formally at war, and most recently with Syrian rebel forces seeking to topple President Bashar al-Assad’s government.

More than 100,000 people have died in the Syrian uprising since Obama in 2011 called for Assad to step down, arguing that he had lost the moral legitimacy to lead the country.

While removing the threat of chemical weapons from the battlefield benefits Syria’s rebels and reduces the chance of a regional war over their use, the deal does not change the basic trajectory of the civil war, in which Assad and his Russian-supplied weapons clearly hold the upper hand against a less cohesive rebel force.

News of the agreement drew immediate criticism from prominent Republicans in Congress, some of whom had supported the idea of airstrikes against Assad after last month’s use of chemical weapons, putting them briefly on the same side as Obama.

“What concerns us most is that our friends and enemies will take the same lessons from this agreement — they see it as an act of provocative weakness on America’s part,” Republican Sens. John McCain (Ariz.) and Lindsey O. Graham (S.C.) said in a statement Saturday. “We cannot imagine a worse signal to send to Iran as it continues its push for a nuclear weapon.”

But other lawmakers responded with a degree of hope, citing Obama’s threat of military force as the catalyst for change.

House Minority Leader Nancy Pelosi (D-Calif.), who was the first congressional leader to endorse Obama’s call for military action, said the agreement “was only made possible by a clear and credible threat of the use of force by the United States.”

Senate Armed Services Committee Chairman Carl Levin (D-Mich.) went further by suggesting that the United States saved face despite being forced to negotiate with the Russian government.

“Russia and Syria sought two things in any agreement: a promise on our part not to use military force, and an end to international support for the Syrian opposition. This agreement includes neither item,” Levin said in a statement. “Just as the credible threat of a strike against Syria’s chemical capability made this framework agreement possible, we must maintain that credible threat to ensure that Assad fully complies with the agreement.”

Support in Congress for Obama’s proposed resolution authorizing military strikes on Syria was uncertain, and the plan allows congressional leaders to continue to postpone any vote on it.

Obama said Saturday that he welcomed the progress that had been made in Geneva, calling it a “concrete step” toward getting Syria’s chemical weapons under international control and, ultimately, destroyed.

“In part because of the credible threat of U.S. military force,” he said in a statement issued by the White House, “we now have the opportunity to achieve our objectives through diplomacy.”

Pentagon spokesman George Little said Navy ships, positioned to carry out a strike if one is ordered, have not been called off.

“The credible threat of military force has been key to driving diplomatic progress, and it’s important that the Assad regime lives up to its obligations under the framework agreement,” Little said.

Senior administration officials said Friday that the Obama administration would not press for U.N. authorization to use force against Syria if it reneges on any agreement to give up its chemical weapons.

Throughout the war, there have been fears that the chemical weapons would fall under the control of radical Islamist groups or that Assad, if he became desperate enough, would sell them to the highest bidder.

Three days of round-the-clock negotiations by U.S. and Russian diplomats and weapons experts yielded a framework for identifying, seizing and destroying an estimated 1,000 metric tons of chemical weapons material by the middle of next year.

Under the agreement, Assad has a week to provide a full accounting of a chemical weapons store he had, until last week, denied possessing. The first international inspection of Syrian chemical weapons is to take place in about two months.

U.S. officials acknowledged that the proposal calls for a destruction schedule that is much more rapid than has occurred in other countries that have voluntarily given up weapons of mass destruction, such as Libya.

The fast pace, officials explained, is in recognition of the ongoing civil war and the need to rid the battlefield of such weapons as quickly as possible.

“These extraordinary procedures are necessitated by the prior use of these weapons in Syria and the volatility of the Syrian civil war,” the framework agreement said.

Syrian rebel commander Gen. Salim Idriss, who angrily denounced the initiative, said that the rebels would facilitate safe passage for international chemical weapons inspectors in Syria but that there would be no cease-fire, vowing to press on “fighting the regime and work [towards] bringing it down.”

Idriss added that Kerry had informed him by telephone that the option of military strikes had not been ruled out.

Syria still denies responsibility for the deaths of more than 1,400 people in an alleged nerve-gas attack last month, and the agreement brokered by Russia on Syria’s behalf assigns no blame.

U.S. officials traveling with Kerry said the United States believes that the Syrian government’s approximately 1,000 metric tons of chemical weapons material is housed among at least 45 sites, about half of which hold material that could be used as weapons.

U.S. intelligence has tracked movement of some of the material during the war, the officials said.

The stockpile contains blister agents such as mustard gas and nerve agents such as sarin, the gas thought to have been used in the August attack, one official said. The officials spoke on the condition of anonymity to discuss some previously classified assessments and to describe the closed-door negotiations in Geneva.

Destruction of the material would take place within Syria and probably also in one or more other countries, another official said.

It is clear that in the U.S. view, the tight schedule for destroying Syria’s chemical weapons, which one official called “daunting,” is partly designed to hold Russia responsible for progress.

It was also clear that the two sponsoring nations disagreed about how the United Nations could enforce the pact.

Details were intentionally left vague. But Russia has not shifted from its long-standing opposition to any U.N. mandate for international military force inside Syria.

That means that punishing Syria for failing to comply with the agreement would probably take the form of U.N. sanctions or other nonmilitary means.

“In this approach that we agreed on, there is nothing said about the use of force, and not about any automatic sanctions,” Lavrov said through an interpreter.

Kerry went out of his way Saturday to praise Lavrov and to thank Russian President Vladimir Putin for pressing ahead with an enforceable agreement despite those differences.

“His willingness to embrace ideas for how to accomplish this goal, and his willingness to send Foreign Minister Lavrov here to pursue this effort, was essential to get to this point,” Kerry said of Putin.

The United States is not taking its threat to use military force off the table, Kerry said, but the agreement appeared to make any such action extremely unlikely.

The Russians had insisted in earlier talks between Lavrov and Kerry that the negotiations could not proceed under the threat of a U.N. resolution authorizing a military strike.

Russia also wanted assurances that a resolution would not refer Assad to the International Criminal Court for possible war-crimes prosecution.

The discussions in Geneva began after a Russian proposal Monday, quickly agreed to by Assad, to place Syria’s chemical arsenal under international control and eventually destroy it.

In New York, a spokesman for U.N. Secretary General Ban Ki-moon said that Syria on Saturday delivered a “formal instrument of accession” to the 1993 Chemical Weapons Convention, meaning it will now be obligated by its terms.

The convention, according to Ban’s spokesman, will enter into force in 30 days, on Oct. 14.

The site of the chemical weapons attack was visited last month by U.N. investigators who are to brief Ban on their findings Sunday.

Wilson reported from Washington. Loveday Morris in Beirut, Colum Lynch at the United Nations, and Karen DeYoung, Ed O’Keefe and Ernesto Londoño in Washington contributed to this report.