Turkey’s 2017 purchase of the first regimental batch of S-400 air defense systems strained ties with the United States. In response, the Donald Trump administration removed Turkey from the F-35 program and imposed sanctions targeting its defense industry and its leaders.
When Turkey acquired the second regimental batch, Washington’s reaction remained restrained. State Department spokesperson Ned Price urged Ankara to avoid deepening ties with Russia’s military-industrial complex, but the reply stopped short of broader punitive steps. Price also declined to say whether the approval process for a potential F-16V Block 70 sale to Turkey would be revisited in light of the second S-400 transfer.
The Turkish defense ministry maintained that no new S-400 contract had been signed, describing the second batch as part of the existing agreement. Ankara signaled openness to future cooperation with Russia on certain components for the S-400, produced by Turkish defense industry entities.
Towards the end of June, signs of a thaw appeared as President Recep Tayyip Erdogan lifted objections to Finland and Sweden joining NATO. At the Madrid NATO summit, U.S. President Joe Biden voiced support for selling F-16 fighters to Turkey and expressed confidence that Congress would approve the deal. A Turkish delegation arrived in the United States for the fourth round of technical talks on a possible F-16 package, with plans for several days of discussions.
Turkey has shown interest in purchasing 40 F-16V Block 70 Viper fighters for about $6 billion and in upgrading Turkey’s existing F-16 aircraft with new air-to-air missiles and avionics at a cost near $400 million, including 80 upgrade kits from the United States. Ankara notes that roughly two hundred F-16 C/D jets currently underpin its air power, highlighting the strategic value of modernizing and expanding its fleet.
Critics in the United States are a minority, though voices persist that oppose the deal. Senate Foreign Relations Committee Co-Chair Bob Menendez has warned against approving the F-16 sale while Turkey continues its S-400 procurement, citing concerns over regional security in the eastern Mediterranean, Greek airspace and Cypriot waters, as well as human rights issues and actions against U.S.-backed groups in northeastern Syria.
Two key points help explain why Washington has ceased public pressure on Ankara over the S-400 issue. First, there is a genuine worry about losing Turkey as an ally and major arms customer, a loss that would be costly on multiple fronts. It is understood that the S-400 contract has been, for now, set in motion and altering course could jeopardize future cooperation in the military-industrial sphere. As a result, restraint and calibrated diplomacy are viewed as more effective than escalatory threats.
Second, U.S. officials aim to secure Turkish access to the S-400 through collaboration rather than confrontation, while Turkish authorities may seek compensation or redress for any sensitive capabilities shared or disclosed. Yet experts argue that only a portion of the system remains accessible, with highly sensitive targeting data unlikely to be transferred. The overall assessment is that most of the critical components and secrets would stay secured within Turkish hands.
In this ongoing dynamic, the broader narrative remains that both sides prefer practical cooperation where possible, while keeping limits on how far their strategic partnership can extend given the S-400 episode. The outcome is not a clean reversal but a pragmatic balance: Washington hopes to keep Turkey aligned with Western defense objectives, and Ankara seeks to preserve sovereignty over its defense procurement while exploring selective collaboration with American and allied partners. This balance is likely to shape upcoming negotiations and regional security calculations for the foreseeable future.