The Syrian opposition wants face-to-face negotiations with the government about a political transition at peace talks that are due to begin in Geneva next week, a leading Syrian opposition politician said on Wednesday.

Salim al-Muslit, spokesman for the High Negotiations Committee (HNC), said there could be no role for President Bashar al-Assad in the transition, saying "the heavy price paid by the Syrian people" would have been wasted if he remained.

Muslit also said the HNC had yet to receive an agenda for the negotiations that are due to begin on Feb. 23 after initial consultations beginning on Feb. 20. He said the negotiations should start with discussion of the transition.

"We want direct negotiations, we want to save time, we want a quick end to the suffering of the Syrian people," he said.

"We now want to get into the essence of the political process - the discussion of the political transition - and what the Geneva 1 communique stipulated about the formation of a transitional body with full powers," he said.

He was referring to the Geneva communique of 2012 calling for the establishment of a transitional governing body with full executive powers that could include members of the present government, the opposition, and other groups. The communique said it should be formed on the basis of mutual consent.

The HNC, which includes rebel groups and political opponents of Assad, has named a 22-member delegation to the Geneva talks.

Diplomacy has repeatedly failed to make any headway towards ending the war that has killed hundreds of thousands of people.

The latest diplomacy effort was launched with Russian and Turkish support after government forces, helped by the Russian air force and Iranian-backed militia, defeated rebels in eastern Aleppo in December - their biggest setback of the war.