Ready for war? Barack Obama and Vladimir Putin set to lock horns over Syria at G20 summit

World's two most powerful men set to face-off over military action in Syria as US President attempts to depersonalise his 'red-line' remarks regarding the alleged use of chemical weapons in the conflict

Barack Obama answers questions during a joint news conference with Swedish Prime Minister Fredrik Reinfeldt (AP)

Vladimir Putin welcomes President Barack Obama and the other heads of the world’s leading and emerging nations to a G20 summit in St Petersburg tomorrow morning. The event will crackle with tensions over the case for punitive strikes against Syria for allegedly using chemical weapons against its own people.

The stage may be set for one of the most awkward and uncomfortable international summits in recent memory with the Syrian crisis likely to dominate discussions and the two heavyweights at the table – Mr Putin and Mr Obama – facing off on the best way forward. A once-planned separate summit between the two men was cancelled by Washington weeks ago.

At a stop-over in Stockholm, Mr Obama said the responsibility to act on Syria was not just his, but the whole world’s. “I didn’t set a red line,” he said at a press conference. “The world set a red line when governments representing 98 per cent of the world’s population said the use of chemical weapons is abhorrent.”

For his part, Mr Putin warned that Russia would consider any strikes ordered without United Nations backing as an act of “aggression”. Nor, he said, would Moscow necessarily stand by if that were to happen. He said: “We have our ideas about what we will do and how we will do it in case the situation develops toward the use of force.”

President Putin may have dropped the temperature slightly, saying in an interview with the Associated Press that Russia would not rule out supporting a UN resolution for action on Syria if evidence were presented proving the use of gas by Bashar al-Assad’s regime. But he also noted that he remains unconvinced by US intelligence.

Tonight, the Russian foreign ministry said its expert findings show that the chemical weapons used in the attack in Syria are similar to ones made by a rebel group.

In Stockholm, Mr Obama was speaking to several audiences at once – to Mr Putin, to the other leaders due to attend the summit, and to politicians back in Washington whose support for the attacks he has called for. The full US Congress is likely to vote on his request next week.

Back in the US, John Kerry, the Secretary of State, and other top members of Mr Obama’s national security team continued their efforts to persuade members of Congress to back the call for military strikes. The situation on Capitol Hill remained fluid, however. While the Senate Foreign Relations Committee today approved strikes, doubts lingered over prospects for the President’s request in the Senate and more especially in the House of Representatives. The impression that Mr Obama wanted to shift responsibility off his shoulders and on to those of Congress did not sit well with everyone in Washington.

“If he chooses to wash his hands of this, you can surely imagine how a vote will turn out,” one top Republican aide on Capitol Hill retorted. Meanwhile a new ABC TV poll showed that nearly two-thirds of Americans are still opposed to strikes.

Mr Putin cited the US invasion of Iraq in 2003 as reason to distrust the case being put forward on Syria. “All these arguments turned out to be untenable, but they were used to launch military action,” Mr Putin said.

And, for his part, Mr Obama acknowledged that those memories were still current in Europe. “I’m very mindful that here in Europe in particular there are memories of Iraq and people being concerned about how accurate this information is,” Mr Obama said.

“I’m somebody who opposed the war in Iraq and am not interested in basing decisions on false intelligence. But, having done a thorough-going evaluation of the information that is available, I can say with high confidence that chemical weapons were used.”