Once the OPCW executive has voted to follow the Lavrov-Kerry plan in a meeting expected early next week, the Security Council is due to give its endorsement of the arrangements - marking a rare consensus after two years of East-West deadlock over Syria.
However, the two powers are divided over how to ensure compliance with the accord. U.S. President Barack Obama has warned that he is still prepared to attack Syria, even without a U.N. mandate, if Assad reneges on the deal.
Russia, which says it is not clear who was behind the Aug. 21 attack and has a veto in the Security Council, opposes attempts by Western powers to write in an explicit and immediate threat of penalties under what are known as Chapter VII powers.
It wants to discuss ways of forcing Syrian compliance only in the event that Damascus fails to cooperate.
But a senior Russian official suggested on Saturday that if there were clear indications that Assad were not committed to handing over chemical weapons, Moscow may stop supporting him.
"I'm talking theoretically and hypothetically, but if we became sure that Assad is cheating, we could change our position," said Sergei Ivanov, chief of staff for President Vladimir Putin.
Ivanov said it would take two to three months to decide how long it would take to eliminate Syria's chemical weapons, a task that the Kerry-Lavrov agreement aims to complete by mid-2014.
The accord has been welcomed internationally because of its potential to remove a toxic arsenal from Syria's battlefield and possibly revive international efforts to press for a political solution to the civil war.
But it has done nothing in the short term to stem fighting with conventional weapons, which has killed more than 100,000 people, according to the United Nations.
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