The Group of 20 comprises finance ministers and central bank governors from 20 major economies: 19 countries plus the European Union, which is represented by the president of the European Council and by the European Central Bank.
Putin refuses to be swayed by Obama over need for military action on Syria
Poison gas attack issue overshadows summit as US president is pressured by Russia and the UN
Reuters in St Petersburg
Barack Obama and Russian President Vladimir Putin failed yesterday to end their bitter dispute over US plans for military action in Syria, as half of the G20 called for a "strong" response to a chemical weapons attack blamed on the regime.
The US signalled it has given up on securing Moscow's support at the UN on the crisis, as Putin reiterated a warning that it would be "outside the law" to attack without the UN's blessing.
The split among leaders of the world's top emerging and developed countries over the issue was symbolised in a statement supported by 11 states at the G20 calling for a "strong international response" to the chemical attack.
Without specifying military action, it said the response would "send a clear message that this kind of atrocity can never be repeated". The signatories included US allies Britain, France and Saudi Arabia.
Obama argued at the end of the summit that the world cannot "stand idly by" after the chemical weapons attack outside Damascus last month which the US claims was launched by President Bashar al-Assad's regime.
Putin has emerged as one of the most implacable critics of military intervention. He and Obama spoke for about 30 minutes on the sidelines of the summit, but neither managed to change the other's mind on Syria.
"He [Obama] disagrees with my arguments. I disagree with his arguments. But we do hear and we try to analyse," Putin said.
Obama also called the discussion "candid and constructive", adding that it "characterises my relationship with him". The US said it had come to terms with the fact that no deal could emerge and signalled that it would take punitive action against Assad's regime without the UN Security Council's backing.
Obama expressed appreciation for France, saying he very much valued President Francois Hollande's "commitment to a strong international response for these grievous acts".
He said he would prefer to have an international mandate for the strikes, but that Washington should not be paralysed by a refusal on the part of some countries to act. "If we're not acting, what does that say?" he asked.
Earlier, Ben Rhodes, Obama's deputy national security adviser for strategic communications said: "We can't have an endless process at the UN Security Council that doesn't lead to anything."
Russia and China - both veto-wielding permanent members of the Security Council - have on three occasions voted down resolutions that would have put pressure on Assad.
UN chief Ban Ki-moon also warned yesterday that military strikes could spark further sectarian violence in the country which he said was suffering from a humanitarian crisis "unprecedented" in recent history.
Adding to the tension in the region, another Russian ship from the Black Sea fleet departed for Syria, the Interfax news agency reported. The landing ship left Sevastopol yesterday for the eastern Mediterranean with a "special cargo", the agency said.