The UN-Arab League envoy to Syria, Lakhdar Brahimi, is to meet President Bashar al-Assad and opposition groups tolerated by the government on his first official visit to the war-torn country.
Brahimi earlier held talks with Foreign Minister Walid al-Moualem, who said he would be backing his mission.
Meanwhile, former envoy Kofi Annan warned there could be no "military solution" to the conflict.
Thousands of people have been killed in Syria since the unrest began in 2011.
On Thursday, Syrian government forces carried out air strikes on Syria's commercial capital, Aleppo.