David Cameron has ruled out any prospect of agreement over Syria at the G20 summit in St Petersburg, saying that Russian president Vladimir Putin remains "miles away" from the truth of Bashar Assad's use of chemical weapons on his own people.
Summit host Mr Putin has rallied opposition from a number of countries at the summit to Barack Obama's proposals for punitive action against Assad, with only France suggesting it will join in any military strikes.
Mr Cameron confirmed that deep divisions over Syria were voiced at Thursday night's four-hour official dinner and said that - despite evidence of nerve gas sarin found by US and UK scientists - Mr Putin is still far from accepting the regime's responsibility for the August 21 attack which killed hundreds of civilians in a Damascus suburb.
"This G20 was never going to reach conclusions on Syria," said the Prime Minister. "The divisions are too great.
"The Russian position that, as Putin has said, if it is proved it is Assad he will take a different view but he is fairly clear that it is the opposition, is miles away from what I think the truth is and miles away from what lots of us believe."
Following a 35-minute face-to-face meeting with Mr Putin in the early hours of Friday, Mr Cameron said: "He says to me that he would like to see further evidence of regime culpability and we will go on providing evidence of regime culpability, as will the Americans and others, but I think it will take a lot to change his mind."
The premiers of Turkey, Canada, Germany and Italy all joined Mr Obama and Mr Cameron in making the case at Thursday night's dinner for a robust international response to Assad's alleged breach of treaties banning the use of chemical weapons.
But it is understood that Mr Putin's argument that any action must be approved by the UN Security Council was backed by several countries, including China.
Hans Blix, who led the UN weapons inspection team in Iraq, told the BBC Radio 4 Today programme: "I think many in the world, including people in the UK, are very anxious that one should not be arrogant and take unilateral action, but actually turn and use the Security Council.
"We have heard that President Putin says that he might even contemplate joining military action. I don't know how sincere that is. But... it is an arrogance to ignore the UN inspectors and to ignore the Council."