(CNN) -- Russia and the United States said Saturday they have reached a groundbreaking deal on a framework to eliminate Syria's chemical weapons, after talks in Switzerland.
Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov stood side by side as they set out a series of steps the Syrian government must follow.
Syria must submit a comprehensive list of its chemical weapons stockpile within one week, Kerry said, and international inspectors must be on the ground no later than November.
President Barack Obama said in a statement that the framework "represents an important concrete step toward the goal of moving Syria's chemical weapons under international control so that they may ultimately be destroyed."
He added, "There are consequences should the Assad regime not comply with the framework agreed today. And, if diplomacy fails, the United States remains prepared to act."
Senior U.S. State Department officials said that according to the timeline, initial inspections of declared chemical weapons sites must be completed by November; all production and mixing and filling equipment must be destroyed by November; and all chemical weapons material must be eliminated by mid-2014.
The best way to ensure international control of Syria's chemical weapons arsenal will be to remove as much as is feasible and to destroy it outside Syria, if possible, the framework document says.
Kerry said the government of Syrian President Bashar al-Assad must allow "immediate and unfettered" access to international inspectors.
He said the inspectors should be able to get to Syria's chemical weapons sites despite the ongoing civil war, provided the al-Assad regime cooperates, since Syria has moved its chemical weapons into areas where it has tight control.
The United States and Russia reached a shared assessment on the amount and type of chemical weapons possessed by the al-Assad regime, Kerry said.
"Providing this framework is fully implemented, it can end the threat these weapons pose not only to the Syrian people but also their neighbors," and the wider world, he said.
Syrian Prime Minister Wael Nader al-Halqi welcomed the deal, saying his country is bent on implementing the political program as the "sole exit" from the crisis, according to the state-run Syrian Arab News Agency.
The verification and destruction process will be carried out under "extraordinary procedures" of the Organisation for the Prohibition of Chemical Weapons, the body that implements the international ban on chemical weapons use, the framework document said.
Russia and the United States will work to get a U.N. Security Council resolution reinforcing the work of the OPCW, it said.
Under the resolution, progress on eliminating Syria's chemical weapons will be kept under review and, "in the event of non-compliance ... the UN Security Council should impose measures under Chapter VII of the UN Charter."
Chapter 7 of the U.N. charter leaves open the possibility for the Security Council to consider the use of force if Syria fails to comply, but Russia, which has veto power on the council, is unlikely to agree to that. Other options include the use of sanctions.
Questioned by reporters, Kerry backed off the idea of force, saying he won't specify what the remedy "might be for circumstances we don't even know yet."
Lavrov said that "any violations of procedures ... would be looked at by the Security Council and, if they are approved, the Security Council would take the required measures, concrete measures."
But, he added, "There is nothing said about the use of force or any automatic sanctions."
Lavrov said it was the responsibility of all parties to ensure that the weapons inspectors can work safely in Syria.
News of the deal came after talks extended into a third day, following late-night discussions Friday.
'Language of diplomacy'
Kerry praised Russia's President Vladimir Putin and Lavrov for seizing the initiative that resulted in the Geneva talks being called on short notice this week.
And he dismissed media speculation that his comment in London on Monday -- when he said that al-Assad could turn over his chemical arsenal to the international community within a week, "but he isn't about to do it and it can't be done, obviously" -- had been a gaffe. That remark prompted Russia to call the talks in Geneva that started Thursday.
"I purposely made the statements that I made in London and I did indeed say it wasn't possible and he won't do it, even as I hoped it would be possible and wanted him to do it," Kerry said. "The language of diplomacy sometimes requires that you put things to the test and we did."
He and Lavrov had discussed the possibility of Syria giving up its chemical weapons before he made that remark, Kerry said, and it was subsequently discussed by Obama and Putin on the sidelines of the Group of 20 meeting in St. Petersburg.
Lavrov said the Geneva talks had achieved the aim discussed in those conversations of putting Syria's chemical weapons under international control.
Syrian opposition fears
French Foreign Minister Laurent Fabius said the U.S.-Russian agreement "constitutes an important step forward," a sentiment echoed by UK Foreign Secretary William Hague.
The two are to meet Monday with Kerry in Paris to discuss the details of the framework and its implementation.
U.N. Secretary General Ban Ki-moon "pledges the support of the United Nations in its implementation," a statement from his spokesman said, and "expresses his fervent hope that the agreement will, first, prevent any future use of chemical weapons in Syria and, second, help pave the path for a political solution to stop the appalling suffering inflicted on the Syrian people."
But the Syrian opposition struck a note of skepticism.
Gen. Salim Idriss, head of the rebel Free Syrian Army, told reporters in Istanbul: "We have information that the regime began to move chemical materials and chemical weapons to Lebanon and to Iraq."
He predicted that al-Assad would keep some of his chemical weapons arsenal, and "then use it against our people and the FSA and then he will come out and accuse terrorists, and he will say that he gave up everything he has."
Also in Istanbul, the Syrian opposition coalition said in a statement that it had elected Ahmed Toma, a moderate Islamist who is one of its members, to head the opposition interim government.
Toma is a dentist and political activist, according to Louay Safi, a spokesman for the National Coalition.
Human Rights Watch reported in 2011 that he had spent 2-1/2 years in prison for his involvement with a pro-reform movement. He replaces Ghassan Hitto, who resigned as interim prime minister in July after failing to form a government.
The Syrian government refers to the opposition fighters as terrorists and has previously accused them of chemical weapons use.
Skepticism that al-Assad will live up to his side of the deal also was voiced by some on the ground in Syria.
In the town of Kafranbel, protesters held up a banner in English saying: "If your case with Assad is only the use of CW, leave him because dying by CW is far better than being bombed by Scuds."
Another banner, in Arabic, read "Kafranbel is quite worried that the international community is giving Assad a license to kill with all kinds of weapons except the use of chemical weapons."
The United States and allies blame al-Assad's forces for the chemical weapons attack outside Syria's capital last month that they say killed more than 1,400 people.
Al-Assad and other officials have vehemently denied their forces were responsible.
The U.N. secretary general is expected to present a report by U.N. weapons inspectors to the Security Council at 11 a.m. ET Monday, three diplomatic sources said. Ban said Friday he believes it "will be an overwhelming report that chemical weapons were used."
Senior State Department officials told reporters that Saturday's agreement "sends a very powerful message" about the use of chemical weapons but acknowledged that the goal of eliminating them in Syria by the middle of next year is "daunting."
The United States and Russia "agree that Syria has a stockpile that includes chemical warfare agents as well as the precursors for those agents," judged to be about 1,000 tons in total, the officials said.
"We agree that it includes blister agents such as sulfur or mustard (gas) as well as nerve agents such as sarin," they said. But the number of locations for these agents has still to be agreed, they added.
On Thursday, Syria told the United Nations that it had sent the paperwork for joining the Chemical Weapons Convention, which bans such armaments. A spokesperson for Ban said the convention would enter into force for Syria on October 14.
Syria then must meet certain stipulations, such as allowing inspections by the body charged with monitoring adherence to the convention. The convention also contains a clause that says those behind chemical attacks should face trial.
But the U.S.-Russia framework calls for an earlier declaration of its chemical weapons stocks and sites than the convention would require.
Obama has threatened to act alone, if necessary, to uphold the international ban on chemical weapons use and his administration credits that threat with Russia's surprise proposal to have Syria turn over its chemical weapons arsenal to international control.
But the U.S. president has also stated his commitment to finding a political solution to the crisis in Syria.
On Friday, Kerry and Lavrov signaled their intent to meet again, on the sidelines of the U.N. General Assembly in New York later this month, with the aim of setting a date to restart long-stalled parallel talks on the broader issue of ending the Syrian civil war.
Outside of the United Nations, U.S. administration officials insisted Friday they would not take the military threat off the table.
A senior defense official said there has been "no change" in the military's planning or readiness levels and commanders have not been instructed to change their "posture" in any way.
Meanwhile, as the diplomatic efforts continue, those on the ground are caught up in the misery of the Syrian conflict.
The U.N. estimates more than 100,000 people have been killed since the civil war began in 2011, in addition to more than 2 million becoming refugees and over 4 million being displaced within Syria.