US president Barack Obama said that the court of world opinon set the red line over the use of chemical weapons by the Syrian regime.

At a joint press conference with Sweden's prime minister, Fredrik Reinfeldt, in Stockholm, Obama said it was not his international credibility on the line.

"I didn't set a red line, the world did," he said. "The world set a red line when world governments said that chemical weapons are abhorrent and passed a treaty saying that. The Congress approved it and set a red line when indicating that in a piece of legislation entitled the Syrian Accountability Act there are things that must be accounted for.

"My credibility is not on the line. The whole international community credibility is, and America and the Congress is on the line because we give lip service to the notion that these international norms are important."

"I believe that Congress will approve it [miiltary action in Syria]," he said

Obama remarked his respect for the UN process over the Syria crisis but said that failure to intervene would increase the possibility of more chemical weapons attack on civilians.

The US president said that Assad regime must be held accountable for the use of sarin gas in the Ghouta region on 21 August.

"I want to build international support for holding the Assad regime accountable," Obama said. "We strongly believe and with high confidence that chemical weapons were used and Assad was the source.

"I respect the UN process but the international community cannot stay silent. That would increase the possibility of more attack and that other countries might use chemical weapons as well."

Obama also said that US and Russian diplomatic relationship had "hit a wall" over Syria.

Obama said it was difficult to get Russia to recognise Assad's crimes at the UN security council.

"Do I hold out hope that Mr Putin will change on some of these issues? I'm always hopeful," Obama said.

Obama also focused on climate change, trade and technology in an attempt to show the world a softer side of American diplomacy. Obama's trip to Sweden marks the first bilateral visit by a sitting U.S. president to the northern European nation.

In August 2012 President Obama issued his now famous'red line' warning to Syria on chemical weapons.

Speaking at an impromptu news conference at the White Hous, he said: "We have been very clear to the Assad regime, but also to other players on the ground, that a red line for us is we start seeing a whole bunch of chemical weapons moving around or being utilized. That would change my calculus," Obama said. "That would change my equation. . . ."