US suspects Syria of chemical attack

US intelligence agencies believe "with varying degrees of confidence" that Syria has used chemical weapons against rebels, the White House has said.

It said the nerve agent sarin had been deployed on a "small scale", and did not say where or when it had been used.

The White House has warned the use of chemical weapons would be a "red line" for possible intervention, but says this intelligence does not represent proof.

Jane O'Brien reports from Washington.