In London, U.S. Secretary of State John Kerry was unmoved by Assad's denial, saying he would be confident going into any courtroom with the evidence gathered by the United States that Syria's government used chemical weapons against its people.
"What does he offer?" Kerry asked of Assad. "Words that are contradicted by fact."
At the White House, National Security Council spokeswoman Bernadette Meehan said, "It doesn't surprise us that someone who would kill thousands of his own people, including hundreds of children with poison gas, would also lie about it."
As the administration stokes its arguments for a limited military strike, President Barack Obama plans an intense round of TV interviews Monday evening and Kerry is returning to Washington from his trip seeking international support. The United States, citing intelligence reports, says the lethal nerve agent sarin was used in an Aug. 21 attack outside Damascus, and that 1,429 people died, including 426 children.
Obama administration officials plan more classified briefings on Capitol Hill. And White House national security adviser Susan Rice is scheduled for a Washington think tank speech timed to the public relations blitz aimed at assuring Americans the administration isn't contemplating another Iraq-Afghanistan style commitment.
The all-points push sets up a prime-time speech by Obama Tuesday night, with votes looming in the Senate as early as Wednesday and likely next week in the House.
In the interview aired Monday on "CBS This Morning," Assad said the evidence about chemical weapons that Kerry is presenting amounts to a "big lie" that resembles the case for war in Iraq that Secretary of State Colin Powell made to the United Nations over a decade ago.
Assad also suggested the rebels fighting his government might be responsible for the alleged gas attack in the Damascus suburbs.
Asked whether he was making a threat of direct military retaliation to any U.S. attack, Assad was vague, saying at one point, "I am not fortune teller to tell you what's going to happen."
"It's not only the government (that's) the only player in this region," he said. "You have different parties. You have different factions. You have different ideology. You have everything in this region now. So you have to expect that."
At a news conference in London with British Foreign Secretary William Hague, Kerry said that if Assad wanted to defuse the crisis, "he could turn every single bit of his chemical weapons over to the international community" within a week. But he said that Assad "isn't about to do it."
Kerry said the U.S. knows "that his regime gave orders to prepare for a chemical attack. We know they deployed forces," Kerry said.
He added: "So the evidence is powerful and the question for all of us is, what are we going to do about it. Turn our backs? Have a moment of silence?"
Meanwhile, Russian and Syrian foreign ministers said they will push for the return of United Nations inspectors to Syria to continue their probe into the use of chemical weapons. Russia's Sergey Lavrov said after Monday's talks with his Syrian counterpart Walid al-Moallem that Moscow will continue to promote a peaceful settlement and may try to convene a gathering of all Syrian opposition figures who are interested in peaceful settlement.
Lavrov said that a U.S. attack on Syria will deal a fatal blow to peace efforts.
Obama plans interviews Monday evening with the network TV newscasts as well as CNN, Fox and PBS.
On Tuesday, he will meet with Senate Democrats about Syria, according to two Senate Democratic aides. The meeting at the Capitol would come just hours before Obama addresses the nation in a prime-time speech on Syria from the White House.
Former Secretary of State Hillary Rodham Clinton, who is scheduled to speak Monday at a White House event on wildlife trafficking, planned to reiterate her support of Obama's efforts to pass the Syria resolution, according to a Clinton aide who spoke on condition of anonymity because the person was not authorized to speak publicly.
Obama and his allies are arguing that the United States needs to remind hostile nations such as Iran and North Korea of American military might while working to reassure the nation that the lessons of the last decade were fresh in their minds.
"It is not Iraq, Afghanistan or Libya," White House chief of staff Denis McDonough said Sunday during one of his five network television interviews. "This is a very concerned, concentrated, limited effort that we can carry out and that can underscore and secure our interests."
But McDonough conceded the administration lacks "irrefutable, beyond-a-reasonable-doubt evidence" that skeptical Americans, including lawmakers who will start voting on military action this week, are seeking.
"It's an uphill slog," said Rep. Mike Rogers, the Republican chairman of the House Intelligence Committee, who supports strikes on Assad. "I think it's very clear he's lost support in the last week," Rogers added, speaking of the president.
A survey by The Associated Press shows that House members who are staking out positions are either opposed to or leaning against Obama's plan for a military strike by more than a 6-1 margin.
"Lobbing a few Tomahawk missiles will not restore our credibility overseas," said Rep. Mike McCaul, the Texas Republican who chairs the House Homeland Security Committee.
Added Rep. Loretta Sanchez, D-Calif.: "For the president to say that this is just a very quick thing and we're out of there, that's how long wars start."
Despite public backing from leaders of both parties to strike, almost half of the 433 current members in the House and a third of the 100-member Senate remain undecided, the AP survey found. They will be the subject of intense lobbying from the administration -- as well as outside groups that have formed coalitions that defy the traditional left-right divide.
Public opinion surveys show intense American skepticism about military intervention in Syria, even among those who believe Syria's government used chemical weapons on its people.
The United States, citing intelligence reports, says the lethal nerve agent sarin was used in an Aug. 21 attack outside Damascus, and that 1,429 people died, including 426 children.
Top administration officials, including Kerry, Defense Secretary Chuck Hagel and U.S. ambassador to the United Nations Samantha Power, planned to brief lawmakers ahead of the Wednesday vote on a resolution that would authorize the "limited and specified use" of U.S. armed forces against Syria for no more than 90 days.
The measure bars American ground troops from combat. A final vote is expected at week's end and the House is expected to take up the issue the following week.
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