“I hope that the Turks will not continue (purchasing) the S-400 and will return to what we consider NATO’s standard practice to not have serious Russian defensive systems,” a senior administration official told reporters, RIA Novosti quoted him as saying.

The official added that Turkey’s participation in the F-35 program in the event of “other significant military purchases” from Russia would be ruled out.

Earlier, Russian Deputy Prime Minister Yuri Borisov said that Turkey showed a "genuine interest" in the purchase of Russian Su-35 and Su-57 fighters.

He also said that there is a high probability of concluding a new contract with Turkey for the supply of Russian anti-aircraft missile systems following the S-400 systems already acquired by Ankara.

In an interview with Nation News, military expert Boris Rozhin praised the statement by Assistant Chief of Staff of the British Air Force Julian Ball that the S-400 air defense system is the most dangerous type of Russian weapon.