Negotiations between Turkey and the United States have been continuing on Ankara’s purchase of Lockheed Martin-made F-16 fighter jets and modernization kits to upgrade its existing warplanes, President Recep Tayyip Erdoğan said Sunday.

The statements by the president came as a confirmation on earlier reports that claimed Turkey is set to acquire 40 new F-16V Block 70 aircraft and nearly 80 kits to modernize its F-16 fighters.

Erdoğan, however, stressed that this purchase cannot be separated from the “F-35 issue” – the stealth fighter jet project from which Turkey was expelled.

The president said Turkey paid $1.40 billion for the F-35s – also produced by the Lockheed Martin company – and that the country needs to receive back its payments since it cannot receive the warplanes.

“The U.S. had such a proposal for the payments,” Erdoğan said, adding that Turkey’s approach regarding the issue is to meet its defense needs with necessary steps. “In particular, we are trying to make our fighter jet fleet ready."

Erdoğan is also expected to hold a meeting regarding the purchase with U.S. President Joe Biden at the upcoming global G-20 summit. There has been no official announcement or meeting scheduled as of yet.

Before expanding the F-16 fleet, Turkey was supposed to acquire fifth-generation F-35 stealth fighters from the U.S.; however, Ankara was expelled from the program – in which Turkish companies also produced parts – over its purchase of Russian S-400 air defense systems. The Russian missile system was purchased after the U.S. refused to sell Turkey its Patriot systems.

Washington argues that the S-400 air missile systems acquired by Turkey could be used by Russia to covertly obtain classified details on the Lockheed Martin F-35 jets and that they are incompatible with NATO systems. Turkey, however, insists that the S-400 would not be integrated into NATO systems and would not pose a threat to the alliance.

Ankara has reiterated on various occasions that its removal from the jet program was illegal and unilateral. It has demanded a fair approach and has said that it is open to negotiations with Washington.

Ankara's purchase of the S-400s also triggered U.S. sanctions. In December 2020, Washington blacklisted Turkey's Presidency of Defense Industries (SSB), its chief, Ismail Demir, and three other employees.

Besides the F-16 jets, Turkey has other domestic programs, including the TF-X National Combat Aircraft (MMU), a fifth-generation stealth fighter jet.

Turkish Aerospace Industries (TAI) is the main contractor of the TF-X MMU program while several other local defense companies contribute to its development.

The TF-X MMU is a fifth-generation jet with similar features to Lockheed Martin's F-35 Lightning II. The domestically built aircraft will be unveiled for the first time on March 18, 2023.