Turkey’s purchase of the advanced S-400 Russian air defense system poses no threat to NATO, Sergey Chemezov, CEO of the Russian Rostec Corporation, stated Wednesday.

Speaking to Russian TV channel RT, Chemezov said that the S-400s are defense weapons and cannot be used in attacks.

"Therefore, I cannot imagine how they can affect NATO countries’ security. On the contrary, the Turkish side ensures the security of NATO countries," he stated.

Ties between NATO allies Turkey and the U.S. were badly strained in 2019 over Ankara’s acquisition of the advanced S-400 Russian air defense system, prompting Washington to remove Turkey from its F-35 Lightning II jet program.

The U.S. argued that the system could be used by Russia to covertly obtain classified details on the Lockheed Martin F-35 jets and said it was 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.

Signaling no change in Washington’s position despite Joe Biden's new administration, Pentagon Press Secretary John Kirby late Tuesday in a press briefing said that, "There's been no change to the administration's policy with respect to the F-35 and the S-400."

"Again, we urge Turkey not to move ahead with the delivery of the S-400. We believe it's incompatible with the F-35, and Turkey remains suspended from that program. Again, we urge them not to retain it," he said.

Kirby argued that Ankara had multiple opportunities over the last decade to purchase the Patriot defense system from the U.S. but "instead chose this S-400, which provides Russia revenue, access, and influence."

Turkey recently inked a consultation agreement with a Washington-based law firm to lobby to protect its rights in the F-35 fighter jet program.

Ankara-based SSTEK Defence Industry Technologies, owned by the Turkish Presidency of Defence Industries (SSB), Ankara's main defense industry authority, signed a contract with Arnold & Porter for "strategic advice and outreach" to U.S. authorities. Reuters reported that the six-month contract was worth $750,000 (TL 5.2 million) and started this month.

Arnold & Porter will "advise on a strategy for the SSB and Turkish contractors to remain within the Joint Strike Fighter Program, taking into consideration and addressing the complex geopolitical and commercial factors at play," the contract said.