Final deals over the new structure were still being hammered out late on Wednesday at a secret meeting in Turkey which brought together a diverse array of rebel units long plagued by deep divisions and bitter rivalries that defy coordination.
"The goal is to get us on track to move towards a unified force, though we are not there yet. Right now, the priority is to create a structured leadership for all the rebels to follow," said Ubada al-Agha, who represents the Sahaba Battalions of Damascus.
But the absence from the meeting of Jabhat al-Nusra, a radical Islamist unit suspected of ties to al-Qaida, threatens to undermine the project.
Though its percentage of fighters is comparatively small, it is one of the most effective forces on the ground and has become increasingly influential among rank and file rebels.
Foreign powers who have thrown their weight behind the 20-month-old uprising have demanded a chain of command before they support the rebels. They are also increasingly wary of financing the insurgency because of the presence of radical Islamists, in addition to concerns about a dangerous lack of discipline.
Complaints are mounting over rebel looting, extrajudicial killings and kidnappings.
One rebel source at the meeting, who declined to be named, said most rebel groups had joined the negotiations, though he was unable to give a detailed breakdown of the attendance.
Jabhat al-Nusra group has already tried to derail the progress of the new internationally recognized umbrella opposition group, the Syrian National Coalition, which is overseeing the talks over the new rebel formation.
Nusra fighters attempted to draw off support by bringing together Islamist battalions in northern Syria and announcing an Islamic state in the region. Most groups renounced their support for this plan soon after meeting with coalition members.Four rebel fronts
A rebel source who spoke to Reuters anonymously said the new structure would likely consist of four "fronts", each to be led by an officer who has defected from Assad's forces and assisted by a rebel commander from the civilian fighters who now make up the bulk of opposition forces.
There would also be a chief of staff, but the source said there was still debate as to who would be named to head the rebels. In addition, a number of representatives would be elected for each "front" to act as local leaders in the chain of command.
Al-Agha said negotiations were still going on and could last late into the night or Thursday.
"It seems we've agreed in general terms to structure. The sticking point is always nominees for positions and what regions get what type of representation," he told Reuters by telephone.
"That is when you have the risk of delegates walking out."
Progress has been helped along, the anonymous source said, by the presence of advisers from foreign countries. Officials were present from Turkey, several Gulf Arab countries and some Western countries, he said, but declined to name them all.
Several other attempts at creating rebel leadership have failed. Leaders of the Free Syrian Army failed to gain the allegiance of many units because its officers remained in Turkey and were accused of funneling cash to favorite rebel groups.
The Joint Leadership of the Military Councils, which has gained support or cooperation from many rebel units on the ground, has fared slightly better thanks to its ability to provide some weapons and even small salaries to those who join.
But it was still unable to enforce discipline in rebel units. It failed to gain the allegiance of many fighting groups, particularly Islamists who have their own channels of funding and often prefer to remain independent.
The success of this latest attempt at rebel restructuring will likely hinge on the willingness of foreign powers to give money or weapons to the new rebel body.
"We have a lot more support from a much wider group of rebels this time, so there is a chance of success," al-Agha said. "But the only way it will truly work is if we get the foreign support we need. Otherwise this effort will be dead before it starts."
BEIRUT (Reuters) -- Syrian rebels are trying to restructure their leadership on a country-wide scale, in hopes of gaining foreign funding for their armed revolt against President Bashar Assad, opposition sources said Wednesday.