"The takeoff of the plane, with a rescue team on board, is set for 9 am Moscow time [5 am GMT]. The Iranian side has already agreed to accept our aid," ministry spokesman Viktor Beltsov said.
The Il-76 freighter will take rescuers and a makeshift hospital to the western province of Lorestan, hit by a powerful earthquake in the morning.
Earlier on Friday, Beltsov said two Il-76s would be dispatched to Iran with tents, blankets, food, electric radiators, and a makeshift hospital under a 1999 intergovernmental agreement on disaster management cooperation.
Friday's magnitude 6.0 quake, preceded by weaker overnight tremors, caused massive destruction in more than 300 villages and towns in Iran's western provinces, leaving at least 70 people dead and more than 1,200 others injured.