The move sends a signal that the US is serious about cutting its NATO ally off from the advanced fighter jet over Turkey's planned purchase of Russia's S-400 missile system.
The United States has halted deliveries to Turkey of equipment related to the F-35 fighter jet, the Pentagon said Monday, ramping up pressure on its NATO ally over the planned purchase of Russia's S-400 missile defense system.
"Pending an unequivocal Turkish decision to forgo delivery of the S-400, deliveries and activities associated with the stand-up of Turkey's F-35 operational capability have been suspended while our dialogue on this important matter continues with Turkey," a Pentagon spokesperson said.
Turkish President Recep Tayyip Erdogan has vowed to move forward with the purchase of the S-400 system despite concern from NATO allies that it will threaten the security of the stealth fighter F-35.
In recent months, the United States has warned that the purchase of Russian system would jeopardize Turkey’s participation in the F-35 program. Turkey has said it expects delivery of the Russian system in July.
The Pentagon's announcement is designed to send a signal to Turkey that it is serious about dropping its NATO ally from the advanced fighter jet program.
To entice Turkey to reverse plans to buy the S-400, the United States has offered the more expensive US-made Patriot system at a discounted price. Turkey has shown an interest in the Patriot system, but not at the cost of breaking its contract with Russia.
It is highly unusual for a NATO ally to purchase Russian military hardware, which is incompatible with allied systems and could provide Russia with valuable intelligence on defense vulnerabilities. In the case of the F-35, the United States and other NATO allies fear the radar on S-400 would enable Russia to learn how to spot and track the $90 million (€80 million) stealth jet.
The US initially planned make the first delivery of two of the Lockheed Martin-made aircraft to Turkey in November. Turkey has been planning to purchase 100 of the fifth-generation jet.
The Pentagon said it was also looking to find alternative sources of supply for the Turkish-produced parts of the F-35. Turkey produces parts of the fuselage, landing gear and cockpit displays.
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The US Congress has also been alarmed by Turkey's planned purchase of the Russian system. Last week, a bipartisan bill was introduced in the Senate that would block transfer of F-35s to Turkey unless it is certified Turkey will not purchase the S-400.
The US decision on the F-35s comes ahead of a NATO summit in Washington this week.
The F-35 issue has added to a series of diplomatic spats between Washington and Ankara, including Turkish demands that the United States extradite Islamic cleric Fethullah Gulen, differences over the war in Syria, and sanctions on Iran.