The international envoy to Syria, Lakhdar Brahimi, has called for the formation of a Syrian national unity government with full executive powers until elections can be held.
Speaking in Damascus, Mr Brahimi said there needed to be "real change" and a swift political end to the crisis, which is estimated to have killed about 45,000 people.
The BBC reports the call was effectively a repeat of the peace plan drawn up in Geneva in June, which got nowhere.
Russian foreign minister Sergei Lavrov added to the envoy's call when he told a senior Syrian diplomat that only dialogue between the government and rebels could end the crisis. He said hopes for a political solution were fading and urged the United States to redouble efforts to make a peaceful settlement.
Rebels have been fighting President Bashar al-Assad's government for 21 months. Opposition groups say more than 44,000 people have been killed.