The White House yesterday launched a big push to rally members of Congress and the American public behind US President Barack Obama's plan for a military strike against Syria.
The US says the government of Syrian President Bassar al-Assad used chemical weapons in an attack on August 21 near Damascus that killed 1,429 people, including more than 400 children, and that a strong response was needed to deter the future use of deadly chemicals.
As a top White House official made the case for a strike during a series of TV interviews yesterday, Assad also used US media to deny he was behind the chemical attack. The Syrian leader's interview with CBS television is due to be shown early today in the United States.
US Secretary of State John Kerry said yesterday they were distributing videos showing the chemical weapons attack to help convince Americans and Congress that a military intervention was necessary.
Speaking in Paris, Kerry said the videos, in which the victims exhibit what appear to be symptoms of nerve gas poisoning, show the attack was not something Americans could ignore.
"Those videos make it clear to people that these are real human beings, real children, parents being affected in ways that are unacceptable to anybody, anywhere by any standards," Kerry said.
"And the United States of America that has always stood with others to say we will not allow this - this is not our values, it's not who we are."
Lawmakers will consider a resolution authorising the "limited and specified use" of US armed forces against Syria for no more than 90 days and barring American ground troops from combat.
A final vote in the Senate is expected at the end of the week. A House vote is likely in the week of September 16.
"The vast majority of members of Congress - House and Senate - are undecided. And that's why the videos are being shown and the briefings are taking place," Kerry said.
Back in the US, the White House was enlisting virtually every senior official from the president on down.
With Obama scheduled to give a national address tomorrow night, his chief of staff, Denis McDonough, began making the White House's case during interviews on five talk shows yesterday, saying the Obama administration was already planning "for every contingency" in case of any fallout from military strikes.
However, McDonough refused to be drawn on whether Obama would go ahead with any strikes if Congress refuses to give military action the green light, nor would he be drawn on any specifics.
"The risks are many fold. One, the risk that somehow we get dragged into the middle of an ongoing civil war," McDonough said on CNN's State of the Union.
"And then there's obviously risk of reaction and retaliation against our friends," McDonough acknowledged.
McDonough also commented on the videos of the attack.
"I hope every member of Congress before he or she decides how to cast a vote will look at the videos. It's unbelievably horrendous," McDonough told Fox News.
Additional reporting by Agence France-Presse