By Andrew Quinn
ZAGREB (Reuters) - The United States called on Wednesday for an overhaul of Syria's opposition leadership, saying it was time to move beyond the Syrian National Council and bring in those "in the front lines fighting and dying".
Secretary of State Hillary Clinton, signaling a more active stance by Washington in attempts to form a credible political opposition to Syrian President Bashar al-Assad, said a meeting next week in Qatar would be an opportunity to broaden the coalition against him.
"This cannot be an opposition represented by people who have many good attributes but who, in many instances, have not been inside Syria for 20, 30, 40 years," she said during a visit to Croatia.
"There has to be a representation of those who are in the front lines fighting and dying today to obtain their freedom."
Clinton's comments represented a clear break with the Syrian National Council (SNC), a largely foreign-based group which has been among the most vocal proponents of international intervention in the Syrian conflict.
U.S. officials have privately expressed frustration with the SNC's inability to come together with a coherent plan and with its lack of traction with the disparate internal groups which have waged the 19-month uprising against Assad's government.
Senior members of the SNC, Free Syrian Army (FSA) and other rebel groups ended a meeting in Turkey on Wednesday and pledged to unite behind a transitional government in coming months.
"It's been our divisions that have allowed the Assad forces to reach this point," Ammar al-Wawi, a rebel commander, told Reuters after the talks outside Istanbul.
"We are united on toppling Assad. Everyone, including all the rebels, will gather under the transitional government."
Mohammad Al-Haj Ali, a senior Syrian military defector, told a news conference after the meeting: "We are still facing some difficulties between the politicians and different opposition groups and the leaders of the Free Syrian Army on the ground."
Clinton said it was important that the next rulers of Syria were both inclusive and committed to rejecting extremism.
"There needs to be an opposition that can speak to every segment and every geographic part of Syria. And we also need an opposition that will be on record strongly resisting the efforts by extremists to hijack the Syrian revolution," she said.
Syria's revolt has killed an estimated 32,000. A bomb near a Shi'ite shrine in a suburb of Damascus killed at least six more people on Wednesday, state media and opposition activists said.
The meeting next week in Qatar's capital Doha represents a chance to forge a new leadership, Clinton said, adding the United States had helped to "smuggle out" representatives of internal Syrian opposition groups to a meeting in New York last month to argue their case for inclusion.
"We have recommended names and organizations that we believe should be included in any leadership structure," she told a news conference.
"We've made it clear that the SNC can no longer be viewed as the visible leader of the opposition. They can be part of a larger opposition, but that opposition must include people from inside Syria and others who have a legitimate voice which must be heard."
The United States and its allies have struggled for months to craft a credible opposition coalition.
U.S. President Barack Obama's administration has said it is not providing arms to internal opponents of Assad and is limiting its aid to non-lethal humanitarian assistance.
It concedes, however, that some of its allies are providing lethal assistance - a fact that Assad's chief backer Russia says shows western powers are intent on determining Syria's future.
Russia and China have blocked three U.N. Security Council resolutions aimed at increasing pressure on the Assad government, leading the United States and its allies to say they could move beyond U.N. structures for their next steps.
Clinton said she regretted but was not surprised by the failure of the latest attempted ceasefire, called by international mediator Lakhdar Brahimi last Friday. Each side blamed the other for breaking the truce.
"The Assad regime did not suspend its use of advanced weaponry against the Syrian people for even one day," she said.
"While we urge Special Envoy Brahimi to do whatever he can in Moscow and Beijing to convince them to change course and support a stronger U.N. action we cannot and will not wait for that."
Clinton said the United States would continue to work with partners to increase sanctions on the Assad government and provide humanitarian assistance to those hit by the conflict.
(Additional reporting by Ayla Jean Yackley; editing by Andrew Roche)