By Susan Heavey
WASHINGTON, Sept 11 (Reuters) - U.S. lawmakers on Wednesday expressed skepticism about the success of an international diplomatic push to get Syria to surrender its chemical weapons arsenal, as deep disagreements remained with Moscow over whether to maintain a military threat.
The diplomatic initiative, kicked off by Syria's close ally Russia as a way to avert military strikes threatened by President Barack Obama, was due to move forward on Thursday when Secretary of State John Kerry meets in Geneva with Russian Foreign Minister Sergei Lavrov.
The talks were open-ended and could go on for several days, according to diplomatic sources. At the heart of the talks will be Russia's opposition to a continued threat of military action that Washington says is needed to ensure Syria complies.
Russia's proposal for Syrian President Bashar al-Assad to surrender his chemical weapons to international control, which has been agreed by Damascus, was seen by Obama as a possible way to avoid a military strike opposed by most Americans.
Obama wants to hold Assad accountable for a suspected chemical weapons attack in a Damascus neighborhood on Aug. 21 that Washington says killed about 1,400 people including 400 children. Syria denies it instigated such an attack.
Bob Corker, the top Republican on the Senate Foreign Relations Committee, said on CNBC he was "1,000 percent supportive of us figuring out the right solution here diplomatically" but he said he had "zero trust" in Russia.
Senator John McCain, a Republican who has been one of the most vocal proponents of a military strike, told a Wall Street Journal breakfast roundtable with reporters that he was not optimistic that diplomacy would succeed.
"Put me down as extremely skeptical," said McCain, who is among a bipartisan group of nine senators seeking to draft a resolution that would be presented to Congress for a vote if a diplomatic agreement is reached.
Under that proposal, U.S. action would depend on a U.N. resolution demanding Assad put his chemical weapons under U.N. international control by a certain date. If he failed to do so, Obama would be authorized to use force.
Other members of Congress said it was vital to maintain the threat of force. Damascus had previously denied it had used such weapons and refused to admit it even had a chemical weapons program.
"Assad and the Russian backers would not have raised that possibility (of scrapping the weapons) if they did not face the threat of military force, and they are unlikely to follow through if the threat does not remain credible," Carl Levin, chairman of the Senate Armed Services Committee, told a meeting of defense reporters.
He backed a provision in the French draft of a U.N. Security Council resolution that would open the way for military action if Syria fails to act on the weapons.
"America must be vigilant and be willing to use force if necessary and Congress should not take the threat of military force off the table," said Senate Majority Leader Harry Reid, a Democrat.
"If there's any indication these (talks) are not serious, if it's a ploy to delay, to obstruct, to divert, then I think we have to again give the president the authority to hold the Assad regime accountable," he said.
The Obama administration kept up its drive to win support for its approach.
U.S. Vice President Joe Biden was to hold two classified briefings at the White House for groups of Republicans from the House of Representatives, and deputy national security adviser Tony Blinken held a classified briefing for all House Democrats, an administration official said.
McCain questioned the decision to have Kerry meet with Lavrov, saying the United States needs to press ahead with more forceful action. "I feel badly, very badly for my friends in the Free Syrian Army today," he told MSNBC's "Morning Joe" program.
"There is nothing more that will drive Syrians into the hands of the extremists than to feel that they have been abandoned by the West."
The rebel Syrian National Coalition has decried the diplomatic proposal as a "cheap trick" that would allow Assad more time to kill Syrians. (Additional reporting by Richard Cowan and Jeff Mason in Washington, Editing by David Storey)