* Assad says U.S. should produce evidence of any attack
* White House seeks to convince reluctant Congress
* U.S. lawmaker says Obama is losing the case
* U.S. does not rule out seeking U.N. Security Council backing
By John Whitesides and Arshad Mohammed
WASHINGTON/LONDON, Sept 8 (Reuters) - Syrian President Bashar al-Assad denied that he was behind a chemical weapons attack on the Syrian people, as the White House on Sunday pressed ahead with the uphill effort of persuading Congress to approve a military strike to punish Assad.
The Obama administration faces a crucial test vote set for Wednesday in the U.S. Senate and White House Chief of Staff Denis McDonough made the rounds of five Sunday talk shows to argue for a resolution authorizing a limited strike on Syria.
In Paris, U.S. Secretary of State John Kerry did not rule out France's suggestion that it go to the U.N. Security Council for an authorization of a possible military strike once U.N. inspectors complete their report on the Aug. 21 attack near Damascus in which more than 1,400 people were killed.
Russia and China, veto-wielding members of the U.N. Security Council, have blocked previous efforts to punish the Syrian government. The United States and France hold that Assad was behind the attack and should be deterred from using chemical weapons again.
Assad denied involvement the attack and said if the United States has evidence, Washington should produce it, CBS reported on Sunday on its news program "Face the Nation."
"There has been no evidence that I used chemical weapons against my own people," CBS reported Assad said in an interview conducted in Damascus. The report was a summary of the interview and did not contain any audio or video of Assad.
Assad said he feared an attack might degrade the Syrian military and tip the balance in the 2-1/2-year-old civil war, CBS reported.
The Syrian president also warned that if there was a military strike by the United States, there would be retaliation by those aligned with Syria, CBS said.
In London, Kerry countered Assad, saying "The evidence speaks for itself."
President Barack Obama faces an uphill climb to persuade U.S. lawmakers returning from a summer recess to vote for military action. During the break, their constituents voiced strong objections to the action, worrying that it would drag the country into another costly, and broader, Middle East conflict.
Opinion polls show most Americans oppose a strike. A recent Reuters/Ipsos poll said 56 percent of Americans believed the United States should not intervene in Syria; 19 percent backed action.
McDonough, the White House chief of staff, led the administration's lobbying effort on Sunday, part of an intensive push for support that will continue on Monday when Obama sits for six network television interviews and culminate with an address to the country on Tuesday night.
"Are there consequences for a dictator who would have used those weapons to gas to death hundreds of children? The answer to that question ... will be followed closely in Damascus, but will also be followed closely in Tehran, among Lebanese Hezbollah, and others. So this is a very important week," McDonough said on the "Fox News Sunday" program.
While Mike Rogers, Republican chairman of the House Intelligence Committee, is a supporter of the strikes, he said Obama had made "a hash" of his argument to punish Assad.
"It's very clear he's lost support in the last week," Rogers said on CBS' "Face the Nation." He said Obama should have called Congress back from its summer break for classified briefings on the proposed strikes, and the administration needed to "regroup."
"The president hasn't made the case," Rogers said.
Representative Jim McGovern, a Democrat from Massachusetts, said that "if I were the president, I would withdraw my request. I don't believe the support is there in Congress." He spoke on CNN's "State of the Union"
Congressional surveys make it clear Obama has a difficult task. A Washington Post vote count showed 223 House members either against or leaning against authorizing the use of military force in Syria. That is more than the 217 needed to block the resolution.
The White House has said the president could go ahead with a military strike without congressional authorization, but has not said he would do so.
French President Francois Hollande, increasingly under pressure at home and among European partners to seek a U.N. mandate before any military intervention in Syria, on Saturday suggested he could seek a U.N. resolution despite previous Russian and Chinese vetoes.
U.N. inspectors are likely to hand in their report later this week roughly at the same time as the U.S. Congress votes on military action. The United Nations has said the inspectors will only determine whether gas was used, not who was responsible for its use.
"On President Hollande's comments with respect to the U.N., the president (Obama), and all of us, are listening carefully to all of our friends," Kerry told a news conference in Paris earlier Sunday. "No decision has been made by the president."
Later, a U.S. official said Washington was not seeking a U.N. vote at this time.
Kerry said key Arab countries were leaning towards supporting a G20 statement - already signed by 12 countries - that called for a strong international response.
The top U.S. diplomat met in Paris with Arab ministers, including from Saudi Arabia, Egypt, Qatar and the United Arab Emirates, following talks in Lithuania with European foreign ministers, who blamed the attack in Syria on Assad but refused to endorse military action.
Iran's new foreign minister, Mohammad Javad Zarif, warned the United States that it would ignite a fire across the Middle East if it attacks Syria.
"We are concerned about warmongering in this region," Zarif told a news conference while on a visit to Iraq. "Those who are short-sighted and are beating the drums of war are starting a fire that will burn everyone."
Underscoring the dangers of the Syrian conflict spreading beyond its borders, an Israeli official said on Sunday the United States would notify Israel hours in advance of an attack on Syria.
While formally on the sidelines of the Syrian crisis, Israel fears coming under reprisals from its northern foe should the United States launch strikes to punish Damascus.
A German newspaper, citing German intelligence, reported that Assad may not have personally given permission for the Aug. 21 attack.
Syrian brigade and division commanders had been asking the Presidential Palace to allow them to use chemical weapons for the last 4-1/2 months, according to radio messages intercepted by German spies, but permission had always been denied, the newspaper Bild am Sonntag said.
This could mean Assad may not have personally approved the attack, intelligence officers suggested.
(Reporting by John Whitesides in Washington and Arshad Mohammed in Paris and London; additional reporting by Rachelle Younglai, David Brunnstrom and Jackie Frank in Washington; Dan Williams in Israel; Natalie Huet in Paris; Alexandra Hudson in Berlin; and Raheem Salman and Yeganeh Torbati in Baghdad; writing by Eric Beech; editing by Jackie Frank)