Barack Obama has begun to prepare a wary US public for military action in Syria in response to the alleged use of chemical weapons, with a flurry of well-publicised meetings with his national security team at the White House.

The comment by the administration that there was “very little doubt” President Bashar al-Assad’s forces had used chemical weapons in an attack which left hundreds dead last week marked a turning point in the US response.

Mr Obama said last year the use of chemical weapons would cross a “red line” in a conflict which the US has stayed out of, apart from promising to send weapons to some anti-Assad forces. However, when faced with allegations that chemical weapons had since been used, administration officials had said they could not be conclusively traced back to Mr Assad’s military.