UN-Arab League peace envoy Lakhdar Brahimi on Sunday urged Syria's warring parties to hold talks "without preconditions" and said he hoped negotiations could take place in Geneva in late November.
In an interview with French-language television channel TV5 Monde, Brahimi also expressed deep frustration with the stalled Syria peace process, admitting he feels like resigning from the post.
Asked during the interview about plans for the UN-backed peace talks in November, Brahimi said: "There is no certainty.
"I am trying to invite everyone for the second half of November.... We'll see. I'm a realist."
World powers are urging Syria's regime and opposition to take part in the long-sought peace talks, which are aimed at launching a political transition to end the country's civil war.
The opposition has said it will not negotiate unless President Bashar al-Assad leaves office, but Brahimi said the condition would have to be set aside.
"We are going to Geneva without preconditions. Mr. Bashar al-Assad cannot say that he does not want to negotiate with 'X' or 'Y' and it's the same thing for the opposition," Brahimi said.
The proposed peace conference -- dubbed Geneva 2 -- would be to decide how to implement a declaration agreed by the major powers in the Swiss city in June 2012 that there has to be a transitional government in Syria.
At least all five permanent members of the UN Security Council -- Britain, China, France, Russia and the United States -- are expected to be involved in the talks and Brahimi said other key countries could take part.
"Iran and Saudi Arabia should be present at Geneva 2," Brahimi said.
He said he had discussed the issue with Iranian President Hassan Rouhani and that while Tehran wanted to be at the talks it was "not the end of the world" if Iran did not attend.
Voicing frustration at the difficulties in getting the two sides to sit down, Brahimi said: "It is almost an impossible mission.
"I feel like resigning because it is very difficult, we are not moving forward, people don't listen to me, but on the other hand, as long as there is a small hope I don't have the right to go."