China has thrown its weight behind the US and Russian plan to eliminate Syria's chemical weapons.
But US President Barack Obama warned that the United States, which has threatened to launch military strikes against Syria in response to chemical attacks, "remains prepared to act."
The ambitious plan to dismantle and destroy Syria's chemical arms by mid-2014 was thrashed out during three days of talks in Geneva between US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov.
China, a veto-wielding permanent member of the security council, welcomed the agreement.
"The Chinese side welcomes the general agreement between the US and Russia. This agreement will enable tensions in Syria to be eased," Foreign Minister Wang Yi said.
The deal has already been rejected by rebel forces who warned it would not halt the Syria conflict.
Announcing the deal on Saturday, Mr Kerry said Syria must provide "immediate and unfettered" access to inspectors from the Organisation for the Prohibition of Chemical Weapons.
"The inspectors must be on the ground no later than November and the goal is to establish the removal by halfway through next year," he said.
Mr Obama said the pressure was now on Mr Assad to deliver, but warmongering Republican senators John McCain and Lindsey Graham said the agreement was a debacle.
"It requires a wilful suspension of disbelief to see this agreement as anything other than the start of a diplomatic blind alley and the Obama administration is being led into it by Bashar Assad and Vladimir Putin," they said.
Mr Kerry said the deal would be encapsulated in a security council resolution drawn up under Chapter Seven of the UN charter, which provides for enforcement through the possible use of military force.
But with Russia strongly opposed to the use of military threats and also wielding a veto on the council, Mr Kerry acknowledged it was "impossible to have a pre-agreement" on what would happen in the event of non-compliance.
Mr Lavrov hailed the accord as an "excellent" agreement "whose significance is hard to overestimate."