ST PETERSBURG, Russia - US President Barack Obama faced growing pressure from world leaders not to launch military strikes in Syria on Thursday at a summit on the global economy that was eclipsed by the conflict.

The Group of 20 (G20) developed and developing economies met in St Petersburg to try forge a united front on economic growth, trade, banking transparency and fighting tax evasion.

But the club that accounts for two thirds of the world’s population and 90 per cent of its output is divided over issues ranging from the US Federal Reserve’s decision to end its program of stimulus for the economy to the civil war in Syria.

Russian President Vladimir Putin wants to use the meeting in a seafront tsarist palace to talk Obama out of military action against Syrian President Bashar al-Assad over a chemical weapons attack which Washington blames on government forces.

Obama wore a stiff smile as he approached Putin on arrival at the summit and grasped his hand. Putin also maintained a businesslike expression. It was only when they turned to pose for the cameras that Obama broke into a broader grin.

The first round at the summit went to Putin as China, the European Union and Pope Francis - in a letter for G20 leaders - aligned themselves more closely with him than with Obama over the possibility and legitimacy of armed intervention.

“Military action would have a negative impact on the global economy, especially on the oil price - it will cause a hike in the oil price,” Chinese Vice Finance Minister Zhu Guangyao told a briefing.

The Pope urged the leaders to “lay aside the futile pursuit of a military solution”. He has also invited the 1.2 billion Roman Catholics and people of other faiths to join him in a day of prayer and fasting on Saturday to end the civil war.

European Union leaders, usually strong allies of the United States, described the August 21 attack near Damascus, which killed an estimated 1,400 people, as “abhorrent” but added: “There is no military solution to the Syrian conflict.”

Putin, Assad’s most important ally, was isolated on Syria at a Group of Eight meeting in June, the last big meeting of world powers. He could now turn the tables on Obama, who recently likened him to a “bored kid in the back of the classroom.” Only France, which is preparing to join US military action, rallied behind Obama. “We are convinced that if there is no punishment for Mr. Assad, there will be no negotiation,” French Foreign Minister Laurent Fabius said before leaving for St. Petersburg.

Putin says rebel forces may have carried out the poison gas attack and that any military strike without Security Council approval would violate international law, a view which is now increasingly openly being supported by others.

Putin’s press secretary, Dmitry Peskov, portrayed the “camp of supporters of a strike on Syria” as divided and said: “It is impossible to say that very many states support the idea of a military operation.”

One national leader attending the summit said there appeared to be little chance of a rapprochement between Putin and Obama, whose relations have soured following Russia’s offer of asylum to former US spy agency contractor Edward Snowden.

Meanwhile, Obama said on Thursday he and Japanese Prime Minister Shinzo Abe shared the view that chemical weapons use in Syria was a violation of international law that must be addressed.

Obama and Abe met on the sidelines of a Group of 20 summit in St. Petersburg as Washington sought to rally international support for a US military strike on Syrian targets. Meanwhile, the United States on Thursday accused Russia of holding the UN Security Council “hostage” over the Syria chemical weapons crisis.

With the White House pushing Congress to approve military strikes on Syria, US ambassador to the United Nations Samantha Power said she could see no way to seek Security Council approval for action against President Bashar al-Assad because of Russia’s blocking.

Amid mounting tensions between Washington and Moscow, Power said Russia’s protection of Assad has put the whole Security Council system of handling international crises under strain.

“Even in the wake of the flagrant shattering of the international norm against chemical weapons use, Russia continues to hold the council hostage and shirk its international responsibilities,” Power told reporters as Russia hosted US President Barack Obama at the Group of 20 summit.

Power, who took over as US envoy to the United Nations one month ago, said the UN Security Council system, in which the five permanent members — Russia, the United States, China, France and Britain — can veto any resolution, had failed the Syrian people.

“Instead the system has protected the prerogatives of Russia — the patron of a regime that has brazenly staged the world’s largest chemical weapons attack in a quarter century,” Power said.

The envoy spoke after US officials briefed other UN members on evidence that Assad’s forces carried out an attack using banned poison sarin gas near Damascus on August 21.

She said the evidence “overwhelmingly” points to an attack by Assad forces.

The United States says more than 1,400 people died in the attack, which the Assad government, supported by Russia, has blamed on Syrian rebels.

Since an uprising against Assad erupted in March 2011, Russia and China have vetoed three western-proposed resolutions that would have aimed to increase pressure on Assad, without imposing sanctions.

The Russian president said this week he would be ready to consider Security Council action if he could be convinced that Assad forces staged the August 21 attack. Power said she did not believe Putin would budge however.

“We have seen nothing in President Putin’s comments that suggest that there is an available path forward at the Security Council,” the US envoy said.

The Obama administration is seeking approval from lawmakers for military strikes, which could be joined by France.

Power’s comments reinforced Obama’s stance that he was ready to order strikes without UN approval. And she stressed US exasperation at the repeated blocking of Security Council resolutions and statements.

The resolutions had been proposed hoping that “our common security and our common humanity might prevail,” she said.

“Unfortunately, for the past two and half years the system devised in 1945 precisely to deal with threats of this nature did not work as it was supposed to. It has not protected peace and security for the hundreds of Syrian children who were gassed to death on August 21. It is not protecting the stability of the region.”

She added: “To stand back would be to endanger not only international peace and security, not only US national security, but, we also believe, the very international system that we have been working these decades to build.”