The Thursday appeal revealed a considerable split within the opposition only weeks before the proposed peace talks in Geneva.

The so-called rebel military council said in a statement that they want half of the seats in the opposition, warning that without strong representation of the militants the group would have no legitimacy.

"We have learned that there have been compromises to expand the coalition which include bringing in a number of politicians, and a similar number from the rebel forces operating on the ground," the statement said.

The militant forces had "requested 50 percent rebel and military representation," it said.

The statement follows a deal struck in Istanbul to admit a liberal bloc of opposition activists into the coalition to dilute the dominance of militants in the organization.

Syria’s anti-government coalition has been facing great divisions in the past months, which were marked by resignation of their president Ahmad Mouaz Al-Khatib in April.

The western-backed coalition, which has been using numerous militant and terrorist groups including al-Qaeda-linked al-Nusra Front to topple the Syrian government, is now facing a challenge with the same groups who want a concrete share.