Iran has given Russian commercial pilots working in the Islamic Republic two months to leave the country as it has no need for them, Transport Minister Hamid Behbahani was quoted as saying on Saturday.

The move is a further sign of strains between Iran and Russia, which has indicated it could back new sanctions against Tehran over its disputed nuclear work. For its part, Iran has voiced frustration over Moscow’s failure to deliver a defense missile system.

Iran’s semi-official Fars News Agency said the idea to order the Russian pilots to leave the country gained momentum after a Russian-made aircraft caught fire as it landed in northeastern Iran in January, injuring more than 40 people.

The plane belonged to Iran’s Taban airline but the pilot was Russian, Fars said. It did not say how many Russians currently worked as pilots for Iranian airlines.

“When our country itself possesses plenty of professional and specialist pilots, there is no need to bring in pilots from abroad,” he told Fars.

Iran has suffered a string of crashes in the past few decades, many involving Russian-made aircraft.

In 2009 a Tupolev aircraft flying to Armenia caught fire in mid-air and crashed, killing all 168 people on board.

U.S. sanctions against Iran have prevented it from buying new aircraft or spare parts from the West, forcing it to supplement its aging fleet of Boeing and Airbus planes with aircraft from Russia and other former Soviet states.

Russia, which has significant trade ties with Iran, is among six world powers trying to find a diplomatic solution to the long-running dispute over Tehran’s nuclear program.