US President Barack Obama has welcomed an agreement between the US and Russia under which Syria’s chemical weapons must be destroyed or removed by mid-2014 as an “important step”.
But a White House statement cautioned that the US expected Syria “to live up to its public commitments”.
The US-Russian framework document stipulates that Syria must provide details of its stockpile within a week.
If Syria fails to comply, the deal could be enforced by a UN resolution.
China, France, the UK, the UN and Nato have all expressed satisfaction at the agreement.
In Beijing, Foreign Minister Wang Yi said on Sunday that China “welcomes the general agreement between the US and Russia.
This agreement will enable tensions in Syria to be eased,” he added.
However, there has so far been no reaction from Damascus.
In the White House statement, President Obama said that the US-Russian deal “represents an important, concrete step toward the goal of moving Syria’s chemical weapons under international control so that they may ultimately be destroyed”.
However the president warned that while the US would continue working with Russia, the United Kingdom, France, the United Nations and others to ensure that destruction-or-removal process was verifiable, there would be “consequences should the Assad regime not comply with the framework”.
“If diplomacy fails, the United States remains prepared to act,” he said.
The Pentagon has backed up the president, saying on Saturday that America was still in position for military strikes.
The US says the Syrian regime killed hundreds in a gas attack last month.
The government of Bashar al-Assad denies the allegations and has accused the rebels of carrying out the attack on 21 August.
Syria recently agreed to join the global Chemical Weapons Convention, and on Saturday the UN said it would come under the treaty from 14 October.
In a joint news conference in Geneva with Russian Foreign Minister Sergei Lavrov, US Secretary of State John Kerry warned President Assad that there must be nothing less than full compliance by his government.
Mr Kerry and Mr Lavrov said if Syria failed to comply, then a UN resolution would be sought under Chapter VII of the UN charter, which allows for the use of force.
However the Russian foreign minister was eager to make clear that force remained a last-ditch option.
“Naturally, no use of force is mentioned in these agreed approaches. Nor are any automatic sanctions mentioned… Any violations must be convincingly and unambiguously proven in the UN Security Council,” he said.
Russia and the US have agreed on an assessment that the Syrian government possesses 1,000 tonnes of chemical agents and precursors, according to a US official.
The US believes the materials are located in 45 sites, all in government hands, half of which have useable quantities of chemical agents.
But it is thought that Russia does not agree on the number of sites, nor that they are all under the government’s control.
The agreement says initial on-site inspections must be completed by November.
It also stipulates that production equipment be destroyed by then, with “complete elimination of all chemical weapons material and equipment in the first half of 2014”.
Mr Kerry outlined six points to the agreement which included Syria placing his chemical weapons under international control within a week and allowing weapons inspectors “immediate, unfettered access” to all sites so that whatever is found can be destroyed.
French Foreign Minister Laurent Fabius, who is visiting Beijing, said it was an “important advance” while British Foreign Secretary William Hague said in a statement: “The onus is now on the Assad regime to comply with this agreement in full.
Analysts however remain divided.
Former British ambassador to Syria Sir Andrew Green said that although there would practical difficulties in implementing the deal, it was a diplomatic coup for Russia and “remarkably good news”.
“[Firstly] it avoids military action, at least for the time being. Secondly it effectively removes the risk of any further use of chemical weapons by the regime. And thirdly and perhaps more importantly, it generates a dialogue and a co-operation with Russia,” he said.
But former US Deputy Secretary of Defence Paul Wolfowitz – along with Republican senators John McCain and Lindsay Graham – was much more sceptical about the deal.
“Whatever gains it brings in terms of reducing the likelihood of additional chemical weapons use, it’s clearly going to come at the price of taking off the table any serious US or western action against the Assad regime, which is a great victory for him and for his Russian and Iranian backers,” Mr Wolfowitz said.
The military leader of the anti-Assad Free Syrian Army has rejected the deal and promised to continue fighting.
“There is nothing in this agreement that concerns us,” said Gen Salim Idriss, describing it as a Russian initiative designed to gain time for the Syrian government.
Mr Kerry is due in Israel on Sunday to meet Prime Minister Benjamin Netanyahu and will then go to Paris to meet his French, British and Saudi counterparts.
Meanwhile there has been more fighting on the ground in Syria with clashes between government forces and rebels in the suburbs of Damascus, including some of the same areas affected by the 21 August attack.
More than 100,000 people have died since the uprising against President Assad began in 2011.
Millions of Syrians have fled the country, mostly to neighbouring nations. However, on Saturday, Italy’s coastguard said more than 500 people, mostly Syrians, had been rescued off the Italian coast.
Millions more have been internally displaced within Syria.