Mr Obama said: “We cannot accept a world where women and children and innocent civilians are gassed on a terrible scale.
“This kind of attack threatens our national security interests by violating well established international norms against the use of chemical weapons by further threatening friends and allies of ours in the region, like Israel and Turkey, and Jordan and it increases the risk that chemical weapons will be used in the future and fall into the hands of terrorists who might use them against us.”
He added: “We’re not considering any open-ended commitment. We’re not considering any boots-on-the-ground approach. What we will do is consider options that meet the narrow concern around chemical weapons.
The US has accused the Assad regime of killing at least 1,429 people including more than 400 children – far more than previous estimates in the alleged chemical attack.