(Updates with National Coalition spokesman comments)

By Dasha Afanasieva

ISTANBUL, Nov 10 (Reuters) - Syria's opposition is edging towards agreeing to international peace talks in Geneva but wants approval from fighters inside the country first to give the process more legitimacy, its spokesman said at talks in Istanbul.

The leadership of the Syrian National Coalition is meeting to agree its stance on the "Geneva 2" talks, which aim to end Syria's two-and-a-half year civil war by creating a transitional governing body.

A draft resolution reaffirms the coalition's commitment to a political solution to the conflict and echoes a declaration in London last month by the Friends of Syria pro-opposition alliance ruling out any role for President Bashar al-Assad in a transitional administration, opposition sources said.

The 108-member coalition is to due vote on the resolution, with 50 percent plus one vote needed for it to pass.

But the opposition said coalition members want to seek the backing of rebel fighting units, community leaders and activists inside Syria for the resolution, to counter criticism that they are out of touch with those battling on the ground. A team will be sent into Syria to gather views.

Major Islamist rebel brigades have declared their opposition to the Geneva process if the conference does not result in Assad's removal and some have said they would charge anyone who attended the planned international talks with treason.

"One delegation will actually be going down to Syria. It's going to be meeting with different FSA (Free Syrian Army) brigades, having a discussion with them around Geneva," said National Coalition spokesman Khaled Saleh.

"If we're going to be in Geneva, they are going to be part of that delegation," he said of the rebel units. The delegation will also meet with civilian groups.

One member of the Syrian National Council, a grouping within the coalition, said that a draft resolution already contained tough conditions for participation in the conference, but those on the ground might want to tighten them further.

That could mean a delay.

While some sources said that a final decision could take up to two weeks, Saleh said it was a "quick process".

"We already started this over the last two weeks. Quite a few of us have been travelling back and forth. A few of these representatives will be coming in the next couple of days," he said.

U.S. envoy Robert Ford met the coalition's senior leadership in Istanbul before their meeting to push them to approve the Geneva talks, coalition members said, and diplomats and other foreign officials said they were optimistic.