The Obama administration is launching an intense 48-hour push to convince Congress and the American people of what it says is the need for a military strike on Syria.
Top security advisers will hold classified and open-door briefings with lawmakers this week. The president will give interviews to six major television networks Monday before making a White House address to the nation Tuesday night.
The administration also is handing out videos to its allies, U.S. lawmakers and broadcasters, showing civilian victims of a chemical weapons attack. U.S. officials say they have evidence that proves beyond any doubt that Bashar al-Assad's army dropped poison gas in the Damascus suburbs last month, killing more than 1,400 people.
U.S. officials say they want to degrade and deter Syria's ability to use chemical weapons again. They say that doing nothing will lead to more poison gas attacks and a wider war.
President Obama has promised to seek congressional approval before responding. But many in Congress call his plan for Syria unfocused, and say it could embroil the United States in another war.
In an interview with CBS television to air Monday, Mr. Assad denies ordering a chemical weapons attack. He says the evidence is not conclusive that such an attack even took place.
U.S. Secretary of State John Kerry says the evidence speaks for itself. Kerry was in Paris Sunday at an Arab League foreign ministers' meeting. He said the ministers agree that Syria's use of chemical weapons was deplorable and that many of them support a G-20 statement calling for a strong international response.
United Nations inspectors plan to issue their report on Syria shortly. Kerry says President Obama has not yet decided whether to wait for the U.N. report before taking action on Syria.