United Nations (UN) Special Envoy for Syria Staffan de Mistura is to arrive in the Iranian capital on Sunday evening, reports suggest, İRNA reported.
In Tehran, de Mistura is to hold talks with several Iranian officials on the issue of Syria.
De Mistura's visit to Tehran is taking place on the eve of the sixth Astana talks on Syria to be held in the upcoming days in the capita of Kazakhstan.
Senior UN envoy is to confer with the Iranian Foreign Minister Mohammad-Javad Zarif and Iran's top negotiator Hossein Jaberi-Ansari on the latest situation of Syria and the peaceful solution for the crisis there.
Since March 2011, Syria has been suffering from unrest and terrorist acts.