Russia has urged Syrian President Bashar al Assad to hand over his chemical weapons to avert a US-led military strike on Damascus.
Russian Foreign Minister Sergei Lavrov called on Mr Assad to put the arms under international control so they could be destroyed to avoid a conflict that he warned would cause an "outburst of terrorism" and spark a new wave of refugees.
He said he had already conveyed the message to his Syrian counterpart, Walid al Moualem, at talks in Moscow, who welcomed the move to "prevent American aggression".
British Prime Minister David Cameron said such a move "would be a big step forward", but warned the international community needed to ensure that discussion of the idea did not become a "distraction" to "the problem on the table".
UN Secretary-General Ban Ki-moon said if inspectors confirmed the use of chemical weapons and Damascus responded "positively" to the Russian proposal, he would propose UN supervised zones in Syria where the country's chemical weapons could be destroyed to overcome what he described as the 15-nation Security Council's "embarrassing paralysis" over the conflict.
Earlier, Mr Assad warned America "to expect everything" if it attacks in retaliation for his alleged use of chemical weapons that killed more than 1,400 civilians.
A Free Syrian Army fighter in Raqqa province, eastern Syria
Speaking in an interview to US television network CBS, Mr Assad denied he was behind the chemical atrocity on August 21 and said the US had provided "not a single shred of evidence" that his forces were involved.
When pressed by CBS correspondent Charlie Rose about what would happen if the US attacked Syria, he replied "every action".
Asked if that could include the use of more chemical weapons, he said: "That depends. If the rebels or the terrorists in this region or any other group have it, it could happen. I don't know. I'm not a fortune teller to tell you what's going to happen..."
America has urged Mr Assad to hand over his chemical weapons, saying it was the only way to stop a military strike against his forces.
US Secretary of State John Kerry made the demand after flying into London for talks with British Foreign Secretary William Hague in the latest stage of his diplomatic tour to garner support for attacking Mr Assad's regime.
He told a news conference at the Foreign Office that the US "was not going to war" with troops on the ground, but was instead planning a "very limited, very targeted, very short-term" strike.
Congress will vote on whether to launch military action in Syria
But, conversely, he added: "Let me be clear, the United States, President Obama, myself, others, are in full agreement that the end of the conflict in Syria requires a political solution. There is no military solution, we have no illusions about that."
He again set out the evidence America claims it has that the Syrian government was behind the Damascus gas attack, saying the "risk of not acting is greater than the risk of acting".
Mr Kerry also stressed the importance of the "special relationship" between the US and Britain and said the two countries were "enormously tied together".
Mr Hague said the US has Britain's "full diplomatic support" and supported "mustering a strong international response" to Mr Assad's alleged use of chemical weapons.
US politicians are set to discuss backing for military action against Syria as President Barack Obama prepares to make a series of TV appearances on six US TV networks later, ahead of delivering a live address to the nation on Tuesday, to push his case.
Congress is set to start debating the issue today and is expected to vote later this week on whether to authorise force against the Syrian regime.
While the White House believes an endorsement from the Senate could be within reach, Mr Obama faces a wall of opposition from both Republicans and from many of his Democratic allies in the House of Representatives.
The White House has refused to state whether Mr Obama, elected in 2008 promising to end foreign wars, would order a strike even if Congress votes "no".