UNITED NATIONS -- The five permanent members of the United Nations Security Council have agreed on a resolution that will require Syria to give up its chemical weapons, but there will be no automatic penalties if the Syrians fail to comply, officials said Thursday.
The agreement, hammered out after days of back-room negotiations, is a compromise among the United States, its allies and Russia about how to enforce the resolution, which would eliminate Syria's chemical arms program.
But the deal, when approved by the 15 members of the Security Council, would amount to the most significant international diplomatic initiative of the Syrian civil war. It would also be a remarkable turn for President Obama, who had been pushing for a military strike on Syria just a few weeks ago before accepting a Russian proposal to have Syria give up its chemical arsenal.
Western diplomats said the resolution would be legally binding and would stipulate that if Syria failed to abide by the terms, the Security Council would take measures under Chapter 7 of the United Nations Charter, the strongest form of a council resolution. Such measures could include economic sanctions or even military action. But before any action could be taken, the issue would have to go back for further deliberations by the Security Council, on which Russia, like the other permanent members, holds a veto.
"This resolution makes clear there will be consequences for noncompliance," Samantha Power, the United States ambassador to the United Nations, said Thursday night.
In an earlier Twitter message, Ms. Power said the resolution established a "new norm" against the use of chemical weapons. Mark Lyall Grant, Britain's ambassador to the United Nations, said in another post that the resolution agreed to by the United States, Russia, China, Britain and France -- the five permanent members of the Security Council -- would be "binding and enforceable."
The diplomatic breakthrough on Syria came as Iran's foreign minister, Mohammad Javad Zarif, said progress had been made toward a resolution of the nuclear dispute between his country and the West, suggesting it could happen in a year.
Mr. Zarif spoke optimistically after emerging from what he called a "very substantive, businesslike" meeting at the United Nations with representatives of the big powers. He also met face to face with Secretary of State John Kerry in one of the highest-level discussions between the estranged countries in years.
The entire 15-member Security Council began to discuss the Syria resolution agreed to by the permanent members of the Security Council on Thursday evening.
A vote on the resolution could come as early as Friday, the French foreign minister, Laurent Fabius, told reporters here Thursday night, as long as the Organization for the Prohibition of Chemical Weapons, based in The Hague, votes on its own Syria measure early Friday. A formal vote on the measure will not take place until the international organization that monitors compliance with the international treaty banning chemical weapons drafts procedures for inspecting and eliminating Syria's vast arsenal of poison gas.
The Syria resolution was a major milestone for the United Nations after years of largely unproductive discussions in the Security Council over the civil war in Syria, which has killed more than 100,000.
Just three weeks ago, the Obama administration grew openly frustrated at the inability to win Russian support for military action against the government of President Bashar al-Assad after a chemical weapons attack on Aug. 21 that killed more than 1,400 people. Ms. Power complained then, "There is no viable path forward in this Security Council."
Now, the council has agreed to a provision in the resolution stating that "the use of chemical weapons anywhere constitutes a threat to international peace and security."
Syria, the resolution states, "shall not use, develop, produce, otherwise acquire, stockpile or retain chemical weapons, or transfer, directly or indirectly, chemical weapons to other states or nonstate actors."
The measure notes that "in the event of noncompliance with this resolution, including unauthorized transfer of chemical weapons, or any use of chemical weapons by anyone in the Syrian Arab Republic," the Security Council can decide to "impose measures under Chapter 7 of the United Nations Charter."
While Western diplomats were praising the new resolution, much will depend on how it is ultimately put into effect in a nation that is caught in a bloody civil war.
According to the resolution, the director general of the Organization for the Prohibition of Chemical Weapons, the watchdog organization that polices the international treaty banning chemical weapons, or the secretary general of the United Nations would report any violations to the Security Council.
The council would then discuss what measures to impose for Syria's noncompliance.
American officials have said they were pleasantly surprised by the completeness of the Syrian government's declaration of its chemical weapons program, which was presented on Friday.
But far more formidable challenges lie ahead.
By November, international monitors are to inspect all of Syria's declared sites, and equipment to produce and mix chemical weapons is to be destroyed, according to a so-called framework agreement that was negotiated by the United States and Russia this month and that is to be enforced by the new Security Council resolution.
Syria's entire arsenal is to be eliminated by the middle of 2014, according to that accord, a process that Mr. Assad has said could take a year.
Skeptics worry that the process may become drawn out, as it was during the 1990s, when the United Nations sought to inspect Saddam Hussein's arsenal in Iraq. Syrian compliance, they fear, may be only partial, and the Russians, they worry, may use their veto power in the Security Council to buy the Assad government more time.
Proponents of the measure say Russia may be cooperative because it shares the West's concern about maintaining zero tolerance for chemical weapons use.
The diplomatic maneuvering over Syria came amid another drama at the United Nations.
Mr. Zarif, Iran's foreign minister, emerged smiling from a meeting with six world powers late Thursday afternoon as American and European officials announced that negotiations on "details" would be worked out in Geneva next month.
The meeting, led by the European Union's foreign policy chief, Catherine Ashton, took place with the five permanent members of the Security Council, along with Germany. Mr. Kerry's separate meeting with Mr. Zarif lasted 30 minutes.
Ms. Ashton said she envisioned an "ambitious timetable" of next steps that would be discussed when the group meets in Geneva next month. The details, she said, will address what Iran needs to do, how soon, and how the international community can verify whether Iran is keeping its word. "Twelve months is a good time frame to think about implementation on the ground," she said.
"It was a substantial meeting," she told reporters here, "a good atmosphere, energetic."
Her attempts in the past to negotiate a settlement with Iran, including a European proposal for a nuclear deal, had not been fruitful. She said Thursday that Iran could choose to respond to her last proposal or submit a new one.
"The purpose of today was to set the tone and the framework," she said.
Mr. Zarif said Iran hoped to reach a détente "in a timely fashion" that would preserve its right to enrich uranium and convince the world that it is for civilian use. "Now we see if we can match our positive words with serious deeds," he said.
He said the "endgame" would be the lifting of all sanctions "within a short period of time."
Somini Sengupta and Rick Gladstone contributed reporting.
This article originally appeared in The New York Times.