The Syrian regime has responded positively to a Russian proposal to place its chemical weapons under international control to avoid a US-led punitive strike.
Foreign minister Walid al-Moallem said he welcomed the plan put forward by his counterpart Sergey Lavrov, under which Damascus would give up its entire chemical stockpile for dismantling.
The plan took a suggestion of Kerry that Syria had a week to give up its chemical arsenal, which was then dismissed by State Department officials, and repackaged it.
Lavrov's words were taken up by UN Secretary-General Ban Ki Moon, who said he was considering asking the Security Council to have the weapons transferred to "safe sites" in Syria for destruction.
The Security Council has been deadlocked because of Russian and Chinese opposition to tighter measures against the regime.
A vote on Lavrov's plan would place in a difficult position the other Security Council members - the US, the UK and France - which have been advocating a military strike against President Basahr al-Assad in response to the Ghouta gas attack.
The plan of putting Assad's chemical arsenal beyond use was first aired by US secretary of state John Kerry hours before President Barack Obama was due to address the nation and make the case for a strike.
In Britain to beef up support for military action, Kerry replied to reporters asking whether there was anything Assad could do to avoid military action. He said that Assad had to turn over all his chemical weapons within a week.
US officials shortly backtracked, saying that Kerry was making a "rhetorical argument" rather than a serious offer. The idea, however, was seized by Lavrov who put it on the table during talks with Moallem in Moscow.
Lavrov said that the weapons had to be destroyed and Syria should become a full member of the Organisation for the Prohibition of Chemical Weapons. He said he expected a quick and positive answer from the regime.
"We do not know if Syria agrees to this but if placing the chemical weapons under international control helps avoid military strikes then we will immediately get to work on this," Lavrov said.
Moallem thanked Russia for "attempting to prevent American aggression against our people".
David Cameron warned that the proposal could have been a "distraction tactic" but admitted that if implemented it would mark a "huge step forward" in reaching a solution to the crisis.
The US State Department said it would take a hard look at Lavrov's proposal but was sceptical.
"The Russians set a trap for John Kerry and he walked into it," Iranian author Amir Taheri commented.
"Great move by Russia re Syrian weapons, perfectly capitalising on a silly Kerry mistake," tweeted Wall Street Journal reporter Tom Gara.