World leaders have held a working dinner to discuss the Syrian crisis, at the end of day one of the G20 summit in the Russian city of St. Petersburg. The informal talks were added as a separate session by summit host, Russian President Vladimir Putin.

U.S. President Barack Obama is being pressed by many global leaders not to launch military strikes in Syria without UN backing. But aides say he'll continue to try to argue his case at the dinner.

Host nation Russia is strongly opposed to military action, while the EU and the BRICS emerging economies, including China, have all warned Obama of the dangers of U.S. military intervention, with the EU saying there's no military solution to the conflict. Aides to Obama have acknowledged that consensus will be hard to reach.

Earlier, the summit's first working session focussed on growth and financial stability.