The US has said that it would punish President Assad for the "brutal and flagrant" chemical weapons attack that it reported killed more than 1,400 people in Damascus last week.
"We cannot accept a world where women and children and innocent civilians are gassed on a terrible scale," President Obama told reporters at the White House.
He said the United States was still in the planning process for a "limited, narrow" military response that would not involve "boots on the ground" or be open-ended. He set no timetable for action.
The US is considering a "limited act" in response to the alleged use of chemical weapons by the Syrian army, but how will Assad respond?
Will America go it alone in Syria after the Government's defeat in the Commons last night? The answer is yes. Emphatically yes.
As the West wakes up to another day, it is not just Prime Minister David Cameron who has a Syria problem - so does President Barack Obama.