* Kerry: there is "no intention" of inserting U.S. ground troops
* Kerry, Hagel say U.S. credibility at stake in Syria
* Boehner, Cantor support use of military force (Recasts with start of hearing)
By Susan Cornwell and Patricia Zengerle
WASHINGTON, Sept 3 (Reuters) - Secretary of State John Kerry said on Tuesday that a resolution in Congress on the use of military force in Syria should not remove the option of using U.S. ground troops, although he stressed there was "no intention" of inserting American soldiers into Syria's civil war.
At the first public hearing in Congress on potential military action in Syria, Kerry said "it would be preferable" not to preclude the use of ground troops to preserve President Barack Obama's options if there was a potential threat of chemical weapons falling into the hands of extremists.
"I don't want to take off the table an option that might or might not be available to a president of the United States to secure our country," Kerry told the Senate Foreign Relations Committee.
The circumstances where troops should be used could be "in the event Syria imploded, for instance, or in the event there was a threat of a chemical weapons cache falling into the hands of al-Nusra or someone else, and it was clearly in the interests of our allies and all of us - the British, the French and others - to prevent those weapons of mass destruction falling into the hands of the worst elements," he said.
Al-Nusra is an al-Qaeda affiliated group that operates in Syria.
Kerry and Secretary of Defense Chuck Hagel were addressing lawmakers as part of the administration's effort to persuade Congress to back Obama's plan to launch limited strikes on Syria for its alleged use of chemical weapons last month.
One of the leading hawks on Syria in Obama's cabinet, Kerry assured lawmakers it would be easy to word a resolution on military force to reassure Congress and the public "there's no door open here through which someone can march in ways that the Congress doesn't want it to, while still protecting the national security interests of the country."
Kerry and Hagel told the committee that any military operation would be limited and specifically designed to degrade President Bashar al-Assad's chemical weapons capability.
Hagel added that a failure to punish Syria for the use of chemical weapons would damage U.S. national security interests and American credibility.
"A refusal to act would undermine the credibility of America's other security commitments - including the president's commitment to prevent Iran from acquiring a nuclear weapon," he said. "The word of the United States must mean something."
OBAMA WINS SUPPORT
As Kerry and Hagel pressed their case for limited military strikes in Syria, Obama won support for action from two top Republicans in the House of Representatives - Speaker John Boehner and Majority Leader Eric Cantor.
"Only the United States has the capability and the capacity to stop Assad and to warn others around the world that this type of behavior is not going to be tolerated," Boehner told reporters. "I believe that my colleagues should support this call for action."
Significant opposition remains in Congress, where many lawmakers, including Obama's fellow Democrats, have said they are concerned the president's draft resolution could be too open-ended and allow possible use of ground troops or eventual attacks on other countries.
The resolution authorizes Obama to use military force as necessary to "prevent or deter the use or proliferation" to or from Syria of any weapons of mass destruction, including chemical weapons.
Obama said on Saturday he would seek lawmakers' approval for a possible military strike, slowing what had appeared to be plans for a swift action. Polls show strong public opposition to U.S. action.
A Reuters/Ipsos poll released on Tuesday showed Obama has failed to convince most Americans of the need for a military strike in Syria. Some 56 percent of those surveyed said the United States should not intervene in Syria, while only 19 percent favored action, the online poll found. (Reporting by Mark Felsenthal, Susan Heavey, Vicki Allen; Writing by John Whitesides; Editing by Alistair Bell and Philip Barbara)