Kerry: Syria chemical weapons attack killed 1,429
30 August 2013 Last updated at 18:43 BST
US Secretary of State John Kerry says the US knows the Assad regime was behind the chemical attack in Damascus, which he says killed 1,429 people.
Mr Kerry said the dead included 426 children, and described the attack as an "inconceivable horror".
The US says it will continue to seek a coalition, and President Barack Obama is meeting his national security team.
The government of President Bashar al-Assad has denied carrying out the attack and blames rebel forces.