Turkey should choose between buying the Russian S-400 surface-to-air missile system or staying a partner in the US's F-35 weapons programme, Republican Senator James Inhofe, the new chairman of the Senate Armed Services Committee, told Bloomberg.
"For Turkey to remain in the F-35 program, it can't move ahead with procurement", Inhofe pointed out.
He described Turkey as an important NATO ally, which he warned should act in accordance with this status.
"The bottom line is: Turkey must make a decision between Russia and the West. If it moves ahead with buying the S-400 from Russia, there will be consequences," Inhofe said.
His comments came after a Pentagon report, which was mandated by Congress, which cautioned that the US administration will "reassess Turkey's continued participation as one of the eight partner nations" in the F-35 programme if Ankara purchases the S-400.
In this vein, Bloomberg also quoted US military expert Steve Zaloga as saying that the US is concerned over Turkey's plans to buy S-400 systems because a number of Russian specialists will be "deployed to the client's country for training and upkeep".
Zaloga also suggested that Ankara may "allow Russian specialists to test out the S-400 radars/sensors against a Turkish F-35 with the ultimate aim of undermining the F-35's counter-radar detection features".
On Saturday, Turkish Foreign Minister Mevlut Cavusoglu said that Ankara decided to buy Russian S-400 systems because Moscow offered "the best deal" when Ankara needed such weapons.
"S-400 is a done deal. We have already finalised this deal and we will buy S-400s from Russia without any question. In the last 10 years we tried to buy [air defence systems] from our American friends, I mean the Patriots, but it didn't work," Cavusoglu emphasized.
His remarks came after Turkey's Anadolu news agency cited a high-ranking source in Washington as saying that the US continues to consider the S-400 air defence system a threat to its F-35 fifth generation stealth fighter platform, and may impose sanctions against Ankara.the S-400 systems to Turkey will start in October 2019. At the same time, he added that the US F-35 fighter jet program is to be continued as planned, with the next jets to be delivered in March of next year.
Last December, Ankara signed a loan agreement with Moscow envisaging deliveries of the Russian-made S-400 air defence systems to Turkey. CEO Sergey Chemezov of Russia's state-owned defence conglomerate Rostec said at the time that the contract envisaged the delivery of four S-400 battalion-size sets worth $2.5 billion, with 55 percent of the contract sum being covered by Russian loans.