The U.N.-Arab League envoy for Syria, Lakhdar Brahimi, arrived in Tehran on Sunday for talks on the Syria crisis with top Iranian officials, media reports said.
The Fars news agency said he would meet President Hassan Rouhani and Foreign Minister Mohammad Javad Zarif and other officials during his three-day visit.
Shiite Iran is Syria's main regional ally and a staunch supporter of President Bashar al-Assad's regime in its struggle against mainly Sunni rebels backed by Western powers and Arab nations.
Tehran is accused of providing military and financial support to Damascus, despite repeatedly maintaining that it has no official military presence in Syria and that its backing takes the form of humanitarian aid.
Brahimi's arrival coincides with Syria's army seizing total control of the strategic town of Yabrud from rebels after a fierce 48-hour-battle.