"Ankara claims to have agreed to purchase the Russian S-400 missile system, which could potentially lead to sanctions under section 231 of CAATSA and adversely impact Turkey’s participation in the F-35 program," Mitchell said in his prepared remarks.
Meanwhile, NATO Secretary General Jens Stoltenberg said on Thursday that Turkey's plans to buy S-400 Triumf air defense missile systems from Russia are the country's national decision. He added NATO believes the acquired weapons should be integrated into the alliance's Air Defense System, which, he said, would be hard to do with S-400.
Despite that, Turkish leader Recep Tayyip Erdogan said at a joint press conference with Russian President Vladimir Putin on Tuesday that Ankara and Moscow had reached an agreement on S-400 and the issue was closed.
In December 2017, Russia and Turkey signed a loan agreement for the supply of S-400 systems to Ankara. According to a statement by the Turkish defense industry secretariat, Ankara acquires two batteries of this system, which will be operated and serviced by the Turkish military personnel.