Syria has handed over information about its chemical arsenal to a UN-backed weapons watchdog, meeting the first deadline of an ambitious disarmament operation that averted the threat of Western air strikes.

The Organisation for the Prohibition of Chemical Weapons said yesterday it had “received the expected disclosure” from Damascus, 24 hours after saying it had been given a partial document from Syrian authorities.

It said it was reviewing the information, handed over after President Bashar al-Assad agreed to destroy Syria’s chemical weapons in the wake of a sarin strike in Damascus’s suburbs last month – the deadliest chemical attack in 25 years.

Washington blamed Assad’s forces for the attack, which it said killed more than 1,400 people. Assad blamed rebels battling to overthrow him, saying it made no sense for his forces to use chemical weapons when they were gaining the upper hand and while UN chemical inspectors were staying in central Damascus.

The timetable for disarmament was laid down by US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov a week ago in Geneva when they set aside sharp differences over Syria to address the chemical weapons issue.

Their plan set yesterday’s deadline for Syria to give a full account of the weapons it possesses. Security experts say it has about 1,000 tonnes of mustard gas, VX and sarin – the nerve gas UN inspectors found had been used in the Aug. 21 attack.

The US State Department said on Friday, after the OPCW announced Syria’s initial declaration, that it was studying the material. “An accurate list is vital to ensure the effective implementation,” spokeswoman Marie Harf said.

Once the OPCW executive has voted to follow the Lavrov-Kerry plan in a meeting expected early this 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. US President Barack Obama has warned that he is still prepared to attack Syria, even without a UN mandate, if Assad reneges on the deal.

Russia, which says it is not clear who was behind the August 21 attack and has a veto in the council, opposes attempts by Western powers to write in an explicit and immediate threat of penalties under what are known as Chapter VII powers.

US President Barack Obama has warned that he is still prepared to attack Syria, even without a UN mandate, if Assad reneges on the deal

It wants to discuss ways of forcing Syrian compliance only in the event that Damascus fails to cooperate.

But a senior Russian official suggested yesterday 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 UN.

Rebel forces, some of whom accused the West of betrayal when Obama deferred air strikes against Assad’s forces three weeks ago, seized several villages south of Aleppo yesterday.

Their offensive was the latest effort to cut Assad’s supply lines to Syria’s biggest city, preventing reinforcements by road from Damascus to the south.

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