UN mediator Lakhdar Brahimi said on Wednesday that he will meet both Syrian delegations separately on Thursday, a day ahead of their first negotiations when he will try to bring them into the same room.

Brahimi, speaking to a news conference after all-day ministerial talks in the Swiss resort of Montreux, first said it was not clear whether he would be able to bring two sides into the same room at the United Nations in Geneva on Friday.

"We will try to see if we meet Friday morning separately and hopefully by Friday afternoon both sides will sit in one room," he said later.

Describing the challenge ahead, Brahimi said: "We have no illusion that it is going to be easy but we are going to try very hard."