"We discussed the deals in Italy and France and ATR officials are expected in Tehran in the coming days to complete the agreement," Asghar Fakhrieh Kashan said.
"There will be 20 firm and 20 optional orders," he added, without specifying the value of the contract.
ATR is co-owned by European aircraft manufacturer Airbus and Italian aerospace group Finmeccanica.
This week, during President Hassan Rouhani's trip to Italy and France, Iran signed a contract for the purchase of 118 Airbus aircraft, to be delivered in the next four years.
Quoted by Iranian media, Kashan said the Airbus deal was worth $10 to $11 billion, while the previously mentioned amount was $25 billion.
The deal is to purchase 73 long-haul and 45 medium-haul Airbus planes, the French manufacturer detailed in a statement.
Before a nuclear deal with world powers took effect this month, Iran's aviation industry was subject to a US embargo preventing Western manufacturers since 1995 selling equipment and spare parts to the Islamic republic.
The sanctions hindered maintenance operations and pinned to the ground part of Iran's ageing fleet -- currently 140 working aircraft, with an average age of about 20 years.
Iran needs 400 to 500 aircraft in the next decade, the head of the Iranian Civil Aviation Authority said in mid-April.