Syria's opposition chief Ahmad Jarba has said his opposition group has agreed to attend an international peace conference only with the aim of removing President Bashar al-Assad from power.
Mr Jarba said in Istanbul after his National Coalition group said it would attend Wednesday's peace conference in Switzerland.
"The Geneva II negotiation table is a one-way road aimed at achieving all the demands of the revolution... and first and foremost stripping the butcher (Assad) of all his powers."
The agreement by the Syrian National Coalition - and the chance of fighters backing the process - will be a boost for Western supporters of the "Geneva 2" talks.
The Geneva 2 talks are seen as the most serious global effort yet to end the near three-year conflict.
Syrian President Bashar al-Assad's government was not immediately available to comment on the prospect of rebel militia representatives playing a role at the negotiations to end fighting that killed more than 100,000 people.
National Coalition spokesman Louay Safi told Reuters the Soldiers of the Levant, the Syrian Revolutionaries Front and the Mujahideen Army all wanted "to have some representation within the delegation" at the talks on Wednesday in Montreux.
It was not immediately clear what role they might play.
Rebel brigades had previously rejected Geneva - demanding the removal of Assad before talks.
Their support is seen as critical if any deals have any chance of being rolled out.
All three are established forces, through restrictions onjournalists in Syria makes it impossible to give independentestimates of their size.
A fourth fighting group, the Islamic Front - thought to be bigger than the other three combined - was still deciding whether to attend, Mr Safi added.
Al Qaeda-linked rebels, increasingly involved in the fighting, have shown no interest in a political process.
The fractured National Coalition itself has little influence on the ground in Syria.
Major Isam el Rayyes, spokesman of the Syrian Revolutionaries Front, confirmed his group was now interested.
"The Syrian Revolutionaries Front and two other major fronts want to be represented at Geneva but we will not send our brigade leaders," he told Reuters.
There was no immediate comment from the other two.
Coalition discussions to appoint a delegation were set to gointo the night. Sources said meetings with the Islamic Front were also taking place in Istanbul.
Government warplanes launched raids on the northern Syrian city of Aleppo and the surrounding countryside, killing 34 people, including five children, the Syrian Observatory for Human Rights said.
Air raids launched by government jets and helicopters left 23 people dead in the city itself, and killed another 11 in the surrounding countryside, the Observatory reported.
It said five of those killed in today's bombing were children.
"Warplanes bombed areas in the neighbourhoods of Tariq al-Bab and Karam al-Jabal in Aleppo," as well as the city's Sukhur district, said the Britain-based monitoring group which relies on a network of activists on the ground for its reports.
The areas are controlled by opposition fighters who have been battling forces loyal to the government of President Bashar al-Assad since they launched a major offensive in the city in the summer of 2012.
The Observatory also said "helicopters dropped explosive-packed barrels on Al-Bab town (east of Aleppo) that led to the death of several fighters from the (jihadist) Islamic State of Iraq and the Levant (ISIL), leaving an unknown number of people wounded.
Helicopters also launched raids with "barrel bombs" on other areas of the northern city, once Syria's commercial capital, and two villages in the south of Aleppo province, said the Observatory without giving further details on casualties.
In December, regime warplanes launched a series of raids with the powerful barrel bombs in Aleppo province, killing more than 500 people in nearly two weeks.
Elsewhere in the country, government jets pounded two areas east of the capital Damascus in eight raids, the Observatory reported, without saying whether there had been any casualties in the attacks.
Meanwhile, the Observatory said that clashes raged between ISIL and rival rebel groups in Aleppo province on today.
Fighters from groups battling the jihadist ISIL seized a village in the province, but lost ground to the other rebels in the town of Manbaj, according to the Observatory.
Nine members of one rebel group taking part in the battle against ISIL were killed early on Saturday, the Observatory reported, when a car bomb went off at a checkpoint they were manning in rural Aleppo.