President Barack Obama is meeting his national security team to discuss possible next steps in Syria.

The White House says the U.S. is still working to establish if President Assad was behind a chemical weapons attack in the country earlier this week.

A top UN official has arrived in Syria to push for access to the scene in Damascus.

Sky's Jason Farrell says there are many barriers preventing an intervention in the conflict.

 Meanwhile the British Foreign Secretary William Hague has said for the first time that the "atrocity" in Syria "was a chemical attack" carried out by Assad forces.

Mr. Hague said that the chances of the attack being a conspiracy by opposition forces was "vanishingly small" and that the only "plausible explanation" for the mass deaths was an attack by the regime.

He said it was essential to get UN inspectors already in the country to the site outside Damascus and that "time was of the essence".

If inspectors were not allowed in, the evidence, he said, would deteriorate.