Why It Matters

Turkey’s push to rejoin the F-35 fighter jet program is testing whether renewed U.S.-Turkey defense cooperation can overcome legal restrictions tied to Ankara’s Russian weapons purchases and broader geopolitical tensions. A recent Congressional Research Service report updated in August details how the Biden administration's focus on Turkey's Russian weapons purchases has given way to the Trump administration's openness to renewed defense cooperation, even as statutory restrictions remain on F-35 transfers.

The stakes are high for U.S.-Turkey relations, which have alternated between close cooperation and notable division. Turkey hosts U.S. forces at Incirlik Air Base, houses a NATO early-warning air defense radar and maintains the second-largest military force within the NATO alliance. However, the country also purchased Russia's S-400 air defense system in 2019, leading to its removal from the F-35 program in July 2019 and sanctions under the Countering America's Adversaries Through Sanctions Act.

Now, with Turkey seeking both F-35 aircraft and sanctions relief, President Donald Trump has expressed openness to an F-35 sale, though the State Department informed some members of Congress in July that Turkey had "not yet met" the conditions for an F-35 transfer.

The Big Picture

Section 1245 of the fiscal 2020 National Defense Authorization Act prohibits F-35 transfers to Turkey unless statutory conditions are satisfied, including that Turkey no longer possesses the S-400 or associated equipment and provides credible assurances that it will not accept the system in the future. As of July, the State Department told members of Congress that Turkey had not yet met those conditions. Yet Trump has expressed openness to an F-35 sale and said during the July NATO summit in Ankara that sanctions would be removed. This tension between existing statutory requirements and the administration's policy preferences has left Congress navigating competing pressures.

Turkey entered into the Mecca Joint Defense Agreement with Saudi Arabia and Pakistan in August, adopting a collective-defense commitment under which an armed attack against one of the three countries is considered an attack against all. Tensions with Israel flared the same month when Israeli aircraft struck an airbase in northern Syria shortly after a Turkish military delegation visited. U.S. Ambassador to Turkey Tom Barrack called the strike an unnecessary escalation.

The country faces annual inflation of about 31.8%, and the Turkish lira has lost more than 92% of its value against the dollar since 2018. Turkey also retains substantial energy and economic ties with Russia, which remains a major supplier of oil and natural gas to the country. That relationship has not prevented Turkey from serving as a diplomatic intermediary in the Ukraine conflict, though Ankara has also refused to join Western economic sanctions against Russia.

In May 2025, a PKK congress voted to disband the organization and end more than four decades of armed struggle against the Turkish government. Turkish authorities imprisoned then-Istanbul Mayor Ekrem Imamoglu in 2025 on corruption-related charges that he and his supporters maintain are politically motivated. A Turkish appeals court later nullified the party congress that elected Republican People's Party leader Ozgur Ozel and provisionally removed him and the party's executive board from their positions.

The Bottom Line

Congress retains substantial authority over a potential F-35 transfer through existing statutory restrictions and its broader oversight of U.S. arms sales. In the House nine members co-sponsored a joint resolution of disapproval seeking to block a related sale of U.S.-origin F110 jet engines for Turkey's domestically produced KAAN fighter, and legislation was introduced in August to tie U.S. arms sales and military aid to verified human rights reforms.

Secretary of State Marco Rubio acknowledged U.S. concerns about developments inside Turkey but said they are balanced with an interest in working with the country on various issues.

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