The US administration and Turkey should explain to the US Congress why Ankara had to buy the Russian S-400  missile system, stated Turksih Foreign Minister Mevlut Cavusoglu, Reuters reported.

According to him, Turkey acquired S-400, as it is “an urgent need” for the country.“NATO is not capable enough to cover our airspace yet."

 “We need to work together and on Syria and other files we have been working together,” Cavusoglu said. “Turkey is supporting the dual track policy of NATO toward Russia, deterrence and dialogue."

He noted that Turkey has proposed to the US that they form a working group to determine that Russian S-400 missile defense systems do not pose a threat to U.S. or NATO military equipment.

“It will not be integrated into the NATO system...therefore we propose the United States to establish a technical working group to make sure that this system will not be a threat - neither to (U.S.) F-35s nor the NATO systems,” Cavusoglu told a panel in the United States.

According to him, Ankara should not choose between Russia and other countries, Anadolu reported.

"We are not choosing between Russia and any other allies," Cavusoglu said at a NATO event in Washington hosted by the Atlantic Council think tank.

"We don't see our relations with Russia as an alternative to our relations with others. And nobody, neither West nor Russia, should or can ask us to choose between."

"Trump himself admitted on the phone that U.S. made the mistake not to sell Patriots to Turkey and he promised Erdogan that he will take care of this issue," Cavusoglu said.

Earlier it was reported that the US has halted supply of equipment related to the stealthy F-35 fighter jet to Turkey. US officials told their Turkish counterparts they will not receive further shipments of F-35 related equipment needed to prepare for the arrival of the stealthy jet. Turkey produces some parts for the fighter.  In Turkey, produced some parts for the fighter: parts of the fuselage, chassis and cockpit displays.

Washington took this step because of the purchase of Russian S-400 air defense systems. The United States and other NATO allies fear the radar on S-400 would enable Russia to learn how to spot and track stealth jet.

On March 28, US senators introduced a bipartisan bill to prohibit the transfer of F-35 fighter aircraft to Turkey until the US government certifies that Ankara will not take delivery of a Russian S-400 air defense system.

F-35 is the fifth-generation combat aircraft. The F-35 first flew on 15 December 2006.