Turkey reiterated that purchasing S-400 missile defense system from Russia is the country's sovereign decision to protect its borders, defying the continuous criticism of the U.S. on the issue.

President Recep Tayyip Erdoğan said on Saturday that the deal has "nothing to do" with NATO, F-35 fighter jets or security of the U.S., but it is rather about the country's independence in terms of making its own regional decisions.

"Everyone knows that this issue has nothing to do with neither NATO and F-35 project nor the security of the U.S.," Erdoğan told a meeting of Turkish Youth Foundation (TÜGVA) in the southeastern Diyarbakır province. The president added that the pressure that Turkey has been facing against buying S-400 air defense system is not about the S-400 itself, but "because Turkey takes action with its own will regarding the regional developments, particularly Syria."

The United States has voiced concern over Turkey's purchase of S-400 air defense systems, urging Ankara to abandon its agreement with Moscow, "eliminating any risk that could harm NATO allies," although the military bloc previously indicated that the acquisition is Turkey's own business.

Regardless of continuous warnings from the U.S., NATO Secretary-General Jens Stoltenberg last April described Turkey's plan to purchase S-400 air defense missile system as a matter of "national decision."

Erdoğan said "it is clear why Turkey is buying this air defense system and how it will use it," adding that this issue will be resolved through logic and common sense.

After protracted efforts to purchase air defense systems from the U.S. with no success, Ankara decided in 2017 to buy Russian S-400 air defense systems.

The move was criticized by the Pentagon, which warned that purchasing the S-400 would hurt Turkish-U.S. relations and Turkey's role in NATO. Ankara is also planning to purchase 100 F-35 fighter jets from the U.S. pending congressional approval, and its pilots are currently training on the weapons platform at Luke Air Force Base in Arizona.

Turkish firms also supply the F-35 program with key components, including airframe structures and essential systems, as well as the center fuselages.

Turkey has been trying to purchase the Patriot air defense system from the U.S. for some time now but was never able to get a commitment from Washington when it was needed the most. As the U.S. failed to meet Turkey's defense needs and endangered losing its NATO ally, Turkey turned to Russia and decided to purchase Russia's S-400 missile system in 2017, which caused a major political impasse between the two countries.