The Syrian opposition on Sunday set preconditions for attending the Geneva II peace conference to negotiate an end to the crisis, set for November 23-24. The summit will attempt to get Syria’s rival sides to agree on a transitional government in that country based on a plan adopted in Geneva in June 2012.

The US and Russia have been trying to bring the Damascus government and Syria’s divided opposition to the negotiating table for months, but the meeting has been repeatedly delayed.

The Western-backed Syrian National Coalition said Sunday that it will attend only if there was a clear time frame for Syrian President Bashar Assad to leave power, adding that Iran’s presence at the conference was unacceptable.

“We have decided not to enter Geneva talks unless it is with dignity, and unless there is a successful transfer of power with a specific timeframe, and without the occupier Iran at the negotiating table,” SNC President Ahmad Jarba said Sunday, quoted by Reuters.

The group has repeatedly said it will only negotiate if it is agreed from the start that President Bashar Assad will leave power at the end of a transition period, whereas many other rebel fighters inside Syria flatly reject negotiating with Assad’s regime. Last week, 19 Syrian rebel groups rejected talks, labeling any participation at the conference “an act of treason.”

On Friday, the UN-Arab League envoy to Syria Lakhdar Brahimi said there would be no Geneva conference if the opposition refuses to attend.

“The participation of the opposition is essential, necessary and important,” he said, adding that the conference was intended “to help the Syrians resolve their problems.”

Last month, Brahimi said that Iran’s presence at the conference was “essential and natural.”

Syria’s conflict, now into its third year, has left over 100,000 dead. It has devastated the economy and the country’s delicate social fabric, has caused 5 million Syrians to flee their homes to other places within the country, and driven another 2 million abroad.