Sergei Lavrov, the Russian Foreign Minister, was to meet John Kerry, the US Secretary of State, in Geneva to discuss the Kremlin's proposal, under which Syrian President Bashar al-Assad would surrender his stockpiles of poison gas to international control.
In meetings planned for this morning and tomorrow, Kerry will prod Moscow to put forward a credible and verifiable plan to inventory, quarantine and destroy Syria's chemical weapons stocks, according to US officials.
Kerry is accompanied by American chemical weapons experts to look at and possibly expand on Russian ideas for the complex task of safely dealing with the vast stockpiles in the midst of a brutal and unpredictable conflict. Russian technical experts will join Lavrov in the meetings.
"Our goal here is to test the seriousness of this proposal, to talk about the specifics of how this would get done, what are the mechanics of identifying, verifying, securing and ultimately destroying the chemical weapons," State Department spokeswoman Jen Psaki said.
The UN-Arab League envoy for Syria, Lakhdar Brahimi, was in Geneva to be available to meet Kerry and Lavrov.
Experts have questioned whether there was any realistic prospect of disarming Syria in the middle of a raging civil war.
"The devil is in the details, and there are a lot of details and a lot of devils," said Adam Ereli, a former US ambassador to Bahrain. "I wouldn't rate the chances very high."
Syria "has one of the biggest chemical weapons programmes in the region and even in the world", said former weapons inspector Dieter Rothbacher. "There are calculations that to secure them, up to 75,000 ground troops are needed. It took us three years to destroy that stuff under UN supervision in Iraq."
Moscow put forward details of its plan to Washington yesterday, but the powers are deeply divided over whether to threaten the regime with the use of force.
France, having been working closely with America, circulated a draft UN resolution that would give Syria just 15 days to declare all of its chemical weapons or risk attack.
The two allies want a clear timetable for Syria to surrender its arsenal, backed by the threat of military strikes. A specific timeline is also a central British demand, according to the Foreign Office. But Russia has ruled out any suggestion of threatening military action. It was unclear whether its plan came with deadlines. The rival proposals followed Obama's White House address to the nation, in which he said that Congress would delay any decision on military action "while we pursue this diplomatic path".
The President said it was too early to tell if the negotiations would succeed and that the US military stood ready to act if diplomacy failed.
His Russian counterpart, Vladimir Putin, asserted in an opinion piece in the New York Times that a potential strike by the US would create more victims and could spread the conflict beyond Syria and unleash a new wave of terrorism.
A vote on France's draft Resolution has been postponed until Russia and the US have completed their Geneva talks and a team of weapons inspectors, who visited the scene of the gas attacks last month, deliver their report to the Security Council. No decision is likely until next week.
The draft resolution proposed by France meanwhile laid out the demands of the Security Council's Western members. It set a deadline of 15 days for Assad's regime to submit a "complete and definitive" declaration of its chemical arsenal.
France demanded the unconditional destruction of these weapons "under international supervision". If Syria failed to comply, the penalty would be "further necessary measures under Chapter VII" of the UN Charter, which provides for the use of armed force.
In addition, the proposed resolution blamed the "Syrian authorities" for the poison gas attacks that claimed hundreds of lives in Damascus on August 21.
The draft would also refer Syria to the International Criminal Court (ICC), opening the way for Assad and his allies to be prosecuted for alleged war crimes.
Lavrov has proposed a weaker presidential statement, a move rejected by the US, Britain and France. A French official close to President Francois Hollande said Russia objected not only to making the resolution militarily enforceable, but also to blaming the alleged chemical attack on the Syrian government and demanding those responsible be taken before the ICC.
The Assad regime was accused by the UN yesterday of perpetrating the worst massacre of the civil war before the chemical weapons attack - in and around the town of Baniyas in May.
In a summary of human rights abuses from April to June this year, a UN commission of inquiry into Syria states that it has "confirmed to its evidentiary standards" that the regime was responsible for the Baniyas slaughter and six other large-scale massacres, with rebels responsible for one.
- additional reporting, AP, Independent