World powers discussed the Syria crisis over dinner at the G20 summit but failed to bridge deeply entrenched divisions over a US push for military action against President Bashar al-Assad's regime, AFP reports.
As tensions over the Syrian conflict threatened to torpedo the working schedule of the G20 summit outside Saint Petersburg, host Vladimir Putin made a last-minute announcement for participants to air their views over dinner.
The leaders took turns over three hours to reiterate their positions on the issue in 10-minute speeches, a diplomatic source close to the talks told AFP.
"The G20 has just now finished the dinner session at which the divisions about Syria were confirmed," Italian Prime Minister Enrico Letta, who attended the dinner, said in a comment on his official Twitter feed.
Russia has led opposition to US-led military action against Assad's regime over a chemical attack on August 21 outside Damascus, which Washington says was perpetrated by Damascus.
In New York, the US envoy to the United Nations accused Russia of holding the UN Security Council hostage.
British Prime Minister David Cameron said London had fresh evidence of chemical weapons use.
In a new bid for a peaceful solution for Syria, the UN announced that its special envoy Lakhdar Brahimi would attend meetings at the two-day summit to push for peace talks.
"Let us remember: every day that we lose is a day when scores of innocent civilians die," the UN quoted Ban as telling the G20 leaders at the dinner.
"Providing more arms to either side is not the answer. There is no military solution."
He also reminded leaders of the humanitarian toll the crisis was taking on neighbouring countries such as Lebanon, Jordan, Iraq and Turkey, paying tribute to their generosity in hosting refugees.
A French diplomatic source said the closed-door dinner, hosted by Putin at the luxurious imperial palace of Peterhof outside Saint Petersburg, was not meant to secure a deal.
"The objective was an exchange between the top world leaders and not to come to an agreement" on the crisis, said the source.
Following the meal, which ended at around 1:00 am (2100 GMT), the leaders of the world's top emerging and developed nations were treated to a rendition of a abridged version of the opera "La Traviata".
Putin and US President Barack Obama put on a show of smiles for the cameras as they shook hands just before the summit got under way on the shores of the Gulf of Finland.
--- 'War cannot solve the problem' ---
Syria's allies remain unmoved by Obama's push.
Iran's supreme leader Ayatollah Ali Khamenei called allegations of an August 21 chemical weapons attack by the regime a "pretext" to launch strikes against the country, and pledged to support Damascus "until the end".
According to US intelligence, more than 1,400 people living in rebel-held suburbs of Damascus were killed in the strike, which involved the use of sarin nerve gas.
"We have just been looking at some samples taken from Damascus in the Porton Down laboratory in Britain which further shows the use of chemical weapons in that Damascus suburb," Cameron told BBC TV from the G20 summit.
A British source told AFP that a soil and cloth sample taken from the site of the alleged chemical attack in the Syrian capital "has tested positive for sarin".
Beyond convincing Russia, Obama has a tough sell ahead elsewhere. China -- another veto-wielding Security Council member -- has already expressed its "grave concerns" over unilateral military strikes.
A political solution is the only way to end the Syria crisis, a senior Chinese official said on Thursday, warning world powers to be "highly prudent".
"War cannot solve the problem in Syria," Chinese delegation spokesman Qin Gang told reporters at the G20.
Pope Francis added his voice to the calls for a peaceful solution, warning against the "futile pursuit of a military solution".
German Chancellor Angela Merkel has repeatedly ruled out her country's participation in any US-led military strike against Assad's regime, while the British parliament has also rejected the idea.
While no formal bilateral sit-down meeting is planned between Obama and Putin, a White House official suggested there would likely be some kind of more informal conversation.
With Russia expected to use its UN Security Council veto to block any military action, US ambassador to the United Nations Samantha Power on Thursday accused Russia of holding the UN Security Council "hostage" over the Syria crisis.
Russia said Syria's Foreign Minister Walid Muallem would travel to Moscow on Monday as Obama seeks to convince US lawmakers to approve military action.
A Western strike against Syria had looked imminent last week, but Obama deferred the move and is seeking backing from Congress when it resumes sitting next week.
Since British lawmakers voted down a bid for strikes against the regime, Washington has found a firm partner in France.
The popular uprising against the Assad regime, now in its third year, has cost more than 100,000 lives.