The United States on Tuesday expressed willingness to welcome Türkiye back into its F-35 fighter jet program if a row over the S-400 air defense system Ankara acquired from Russia is resolved.

"If we could get through this S-400 issue, which we would like to do, the U.S. would be delighted to welcome Türkiye back into the F-35 family," Deputy Secretary of State Nuland said during a visit to the country.

"But first, we need to resolve this other matter and ensure that Türkiye maintains a robust air defense while doing so," Nuland told private broadcaster CNN Türk.

Türkiye sought to purchase Lockheed Martin's F-35 fighter jets, but the U.S. imposed sanctions, known as CAATSA, and removed it from the multinational program to buy and help develop and build the warplane in 2019 after it acquired S-400s from Russia.

Washington argued the air missile defense systems posed a risk to the advanced fighter jet, whereas Ankara insisted they would not be integrated into NATO systems.

Türkiye had ordered about 100 F-35s and its companies were building some 900 parts for the fighter jet.

"If we can get through this issue, then the CAATSA issue will go away, and we can get back into an F-35 conversation," Nuland said.

F-16s a priority for U.S.

Türkiye has demanded reimbursement for payment it had made for the F-35s and has since requested to buy F-16 warplanes and modernization kits to refresh its existing fleet.

After a prolonged process that frustrated Ankara, U.S. President Joe Biden's administration last Friday finally approved the $23 billion sale of 40 new F-16s, as well as nearly 80 kits after Türkiye formally ratified Sweden's membership in NATO.

The Biden administration had repeatedly supported the sale, but several lawmakers in Congress had tied the sale to Türkiye's approval of Sweden's NATO bid.

President Recep Tayyip Erdoğan eventually also made Sweden's membership contingent on approving the sale of the new planes. Türkiye formally ratified the Nordic country's membership in the military alliance last week.

The U.S. Congress has 15 days to object to the sale, after which it is considered final.

Nuland emphasized that her visit coincided with Türkiye's approval of Sweden's NATO membership and said that the purpose of her visit was to "revitalize" the relations between the two countries.

She said efforts were being made to convince American lawmakers that enhancing Türkiye's F-16 fleet is very important for American security.

Nuland stressed that Türkiye's acquisition of the F-16s is a priority for the U.S.