Sources tell CNN’s Barbara Starr that the Pentagon and US intelligence services are consulting with Syria's neighbors Turkey, Israel and Jordan about what to do if it looks like Assad is about to launch a chemical attack on his own people.
A senior US official says all the allies are now considering how to keep Syria from putting chemical warheads on its artillery or missiles.
But an airstrike to stop it, could cause havoc if residual chemicals escape.
What if Assad leaves? US officials say they have long been planing for 'the day after Assad" – such as training Jordanian troops to provide security – but for now they just hope Syrians troops will keep those chemical weapons under lock and key.