U.S. Secretary of State Hillary Clinton says that is crucial for Syrians to unite in support of political change.

“They must come forward with a unified position, a vision if you will, of the kind of Syria that they are working to build," she said. "They must be able to clearly demonstrate a commitment to including all Syrians and protecting the rights of all Syrians.”

The Syrian National Council is the largest opposition group to emerge from the year-long government crackdown on dissent. 

"This new government will represent everyone in Syria," said SNC spokesman George Sabra. "The Syrian president will be elected freely, either by the parliament or by the people. This elected government will assure the independence of the legal system and also assure the rights of individuals and groups."

Middle East analyst Steve Heydemann says the diversity of Syria's opposition complicates agreement on a common strategy, especially in the midst of armed conflict.

“There are a huge number of groups with very different priorities and agendas that define the Syrian opposition," said Heydemann. "So bringing them together under an umbrella like the Syrian National Council and expecting that they would easily or quickly move toward some kind of coherent set of goals and objectives is probably a little bit unrealistic.”

With government forces driving back opposition fighters, the Friends of Syria group is urging closer cooperation between civilian and military leaders of the uprising to help rally skeptical civilians to their cause.

“I think the international community is concerned that the opposition has been a bit too vague about what the future of Syria might look like," he said. "And that uncertainty has kept a lot of Syrians on the sidelines - people who might support the opposition if they were confident about what a post-Assad Syria would mean for them.”

The United States and Turkey are considering non-lethal assistance for the uprising in hopes of building momentum for President Assad's opponents as U.N. and Arab League envoy Kofi Annan pushes a Russian-approved peace plan for a cease-fire and humanitarian assistance.

The Syrian government this week accepted the Annan plan. But Western diplomats and the Syrian opposition are skeptical about any plan that doesn't call for Assad to leave power.