Syria's key opposition National Coalition on Wednesday urged UN-Arab League envoy Lakhdar Brahimi to remain neutral, after he cited opposition divisions over new delays to peace talks.
The statement comes a day after Brahimi said intensive talks on a mooted peace conference in Geneva had failed to produce a final date for the long-planned discussions.
"The Syrian National Coalition confirms that the mission of the joint UN-Arab League envoy -- as understood by the Syrian people -- is to seek to achieve their legitimate aspirations and lift their suffering, or to remain neutral at the very least," the Coalition said a statement.
The statement accused Brahimi of seeking to "blame" the opposition for his failure to convene the conference, urging him to "adhere to neutrality and not stray from what is acceptable in political discourse".
The comments come after Brahimi announced that no date had been set for peace talks despite renewed suggestions that a conference could take place in November.
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"We were hoping that we'd be in a position to announce a date today, unfortunately we're not," Brahimi told reporters in Geneva on Tuesday.
"But we're still hoping that we'll be able to have the conference before the end of the year," he said, adding he would meet again with Russian and US officials on November 25.
Pressed to reveal the main stumbling blocks, Brahimi cited divisions within the Syrian opposition, saying he hoped they would "move towards the formation of a credible delegation" for peace talks.
"That will be a big step forward to make the conference possible," the Algerian veteran international mediator said.
The Coalition is due to meet in Istanbul on Saturday to discuss participation in any peace talks, but faces opposition from a key group which has threatened to quit the grouping if it takes part.
The opposition wants President Bashar al-Assad's departure from power to be a condition of any peace talks, but the regime has said the president's role will not be on the table.