President Obama refuses to say if strikes on Syria will go ahead without Congress's backing as G20 summit draws to a close

Obama and Putin held surprise meeting over Syria, it was revealed during press conference

US President Barack Obama told reporters at the G20 summit in St Petersburg that he would try to convince the American public of the need to act against the Syrian government. (AFP/Getty)

“I put it before Congress because I could not honestly claim that the threat posed by Assad's use of chemical weapons on innocent civilians and women and children posed an imminent, direct threat to the United States,” Mr Obama told reporters at the G20 summit in St. Petersburg.

Mr Obama said he understood the US public's scepticism about action against Syria, but added that he was confident he could persuade them that the use of chemical weapons requires a military response.

The president said he needed to convince the nation that his plans would be “limited and proportional” and designed to uphold international norms.

Meanwhile the leaders of eleven of the G20 member states called for a strong international response to the alleged 21 August attack in Syria, according to the White House. However, the countries have stopped short of calling for a military response.

“The evidence clearly points to the Syrian government being responsible for the attack, which is part of a pattern of chemical weapons use by the regime,” said the statement, released as the G20 summit was ending.

“We call for a strong international response to this grave violation of the world's rules and conscience that will send a clear message that this kind of atrocity can never be repeated. Those who perpetrated these crimes must be held accountable,” it said.

The statement was signed by the leaders and representatives of Australia, Canada, France, Italy, Japan, South Korea, Saudi Arabia, Spain, Turkey, Britain and the United States.

It was also today revealed that Mr Obama and Russian leader Vladimir Putin held a private meeting to discuss their differences over how to respond to chemical weapons use.

Mr Putin told reporters that the pair had spoken for 20-30 minutes and that while they had disagreed, the meeting was constructive.

Turkish Prime Minister Tayyip Recep Erdogan said that “almost all” leaders at the summit accepted the need for some form of intervention in Syria, repeating that a small coalition could be formed, even outside the auspices of the UN, for a joint operation.

Ankara has previously said that Turkey would be ready to take part in some form of international action against Syrian President Bashar al-Assad. Its armed forces are placed on alert to guard against threats from Syria, with which it shares a 900km (560-mile) border.

“Almost all the leaders who attended the summit are closely following the massacre the Syrian regime carried out on its people and the leaders have expressed that an operation is extremely necessary against Damascus,” Mr Erdogan said.

Prime Minister David Cameron echoed Mr Erdogan's sentiments. Despite the failure to gain MPs' support for a potential UK military intervention, Mr Cameron said that the international community cannot “contract out” its morality by allowing Russia to block intervention in crises such as that engulfing Syria.

He also stressed that backers of direct reprisals against the Syrian regime had made a “powerful” case at the summit, despite failing to overcome Mr Putin's opposition.

Additional reporting by PA