The United States will press forward with ending Turkey’s role in producing parts for the F-35 Joint Strike Fighter, Air Force secretary nominee Frank Kendall said at his Senate confirmation hearing Tuesday.

Turkey was officially kicked out of the F-35 program in 2019 under the Trump administration for agreeing to purchase Russia’s S-400 air defense system in 2017. U.S. officials had repeatedly warned the purchase would jeopardize Turkey’s role in the multinational fighter program because operating both systems could expose F-35 vulnerabilities to Russia.

The Biden administration had renewed efforts to try and get Turkey to reverse course as recently as this March, but Turkish Foreign Minister Mevlut Cavusoglu told Secretary of State Anthony Blinken the purchase was a “done deal,” Voice of America reported.

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Turkey is also banned from obtaining any of the fighters it had previously ordered.

“Under the current situation with Turkey, I think we should not be making F-35 parts in Turkey,” Kendall said, telling Sen. Jeanne Shaheen, D-N.H., that if confirmed he would see that the production is halted as soon as possible.

Turkey is a member of NATO, and the potential integration of the S-400 platform into the alliance’s defense architecture had concerned other member countries.

Read more: Defense One