A Syrian opposition official says the main opposition group is staying away from peace talks until they get a response to their demands from the United Nations.

Basma Kodmani, a member of the opposition's negotiations team, says they are still waiting for response from the U.N. regarding lifting the sieges on rebel-held areas and an end to Russian and Syrian bombardment.

Opposition officials say they will not join the Geneva talks unless these demands are met.

The talks were scheduled to begin in Geneva on Friday and the Syrian government delegation is expected later in the day.

The U.N. special envoy to Syria Staffan de Mistaura said Thursday that the peace talks he plans to launch in Geneva "in the next few days" are an opportunity not to be missed.