U.S. Undersecretary of State Victoria Nuland said the U.S. would impose further sanctions if Turkey bought additional major arms systems from Moscow, according to Reuters.

Washington says the S-400s pose a threat to its F-35 fighter jets and to NATO’s broader defense systems.

Turkey rejects this, saying S-400s will not be integrated into NATO and purchasing them was a necessity as it was unable to procure air defense systems from any NATO ally on satisfactory terms.

Former President Donald Trump imposed sanctions on Turkey’s defense procurement agency in December after Ankara acquired the Russian air defense system in 2019 and began testing it.

Turkey has called on the United States to hold talks to find a mutually acceptable solution to its possession of the S-400s that would both meet its defense needs and allay Western concerns that the system threatens NATO’s defenses. The United States had offered its NATO ally an option to purchase the Patriot air defense system instead but talks snagged over Turkey’s insistence on technology transfer.

The Turkish authorities are in talks with Russia to buy more of the missiles.

This week, the head of Russia's main arms export agency announced that Moscow was in the process of completing consultations for a contract to deliver the second batch of S-400 missiles to Turkey, TASS news agency reported on Tuesday.

Rosoboronexport CEO Alexander Mikheyev told reporters at the MAKS-2021 air show that Russia expects to complete the work in the coming months.

"Final consultations are underway, a financial model has been put together, as well as a program for technical cooperation on the project," Mikheyev said.

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