"The delegation from our country will travel to Russia tomorrow to attend the aviation salon [MAKS]," the source said adding that the sides will discuss the supply of S-300 systems to Tehran during the first days of the visit.
"The exact delivery dates will be clarified upon the delegation's return," the diplomat said.
The International Aviation and Space Salon MAKS 2015 will be held in the town of Zhukovsky near Moscow between August 25 and 30.
In 2007, Russia and Iran signed an $800-million deal for the delivery of five S-300 battalions. Moscow suspended the deal after the UN Security Council imposed an arms embargo on Tehran amid suspicions that it was trying to facilitate nuclear weapons development.
Earlier in the day, Iranian Defense Minister Hossein Dehghan expressed hope Tehran would be able to receive S-300 missile defense systems from Russia by the end of 2015.