President Barack Obama issued a blunt challenge to sceptical US lawmakers yesterday to approve his plan for a military strike on Syria, saying inaction would put America’s prestige and their own credibility at risk.

Using a visit to Sweden to build his case for military action, Obama insisted that the world could not remain silent after the “barbarism” of the August 21 chemical weapons attack he blamed on the forces of Syrian President Bashar al-Assad.

“My credibility is not on the line. The international community’s credibility is on the line,” Obama told a news conference in Stockholm.

“And America and Congress’ credibility is on the line, because (otherwise) we give lip service to the notion that these international norms are important.”

One day before travelling to St Petersburg for a G20 summit hosted by Vladimir Putin where Obama will look to persuade other world leaders over Syria, he said he held out hope that the Russian President would back away from his support for Assad.

Putin said any strike on Syria would be illegal without UN support.