Ankara, Turkey – Turkey will not turn back on its purchase of Russian S-400 missile defense systems and will take reciprocal steps after evaluating unjust US sanctions imposed over the acquisition, Foreign Minister Mevlut Cavusoglu said on Thursday.

The United States on Monday imposed sanctions targeting NATO member Turkey’s Defense Industry Directorate (SSB), its chief, Ismail Demir, and three other employees over its purchase of the S-400s. Turkey condemned unjust US sanctions as a “grave mistake.”

President Tayyip Erdogan said on Wednesday unjust US sanctions were a “hostile attack” against Turkey’s defense industry, and they were bound to fail.

Foreign Minister Cavusoglu said Turkey could not be subjected to so-called CAATSA sanctions as its acquisition predated the law, adding that the decision was an attack on Turkey’s sovereign rights and would have no impact.

The 2017 Countering America’s Adversaries through Sanctions Act (CAATSA) legislation is meant to dissuade countries from buying military equipment from NATO foe Russia.

“This is not in line with international law, diplomacy, and it is a politically and legally wrong decision,” Cavusoglu said, adding that the United States could have solved the dispute with common sense if it cooperated with Turkey and NATO.

“If there was to be a step back, it would have happened by now,” he said, referring to the decision to acquire the S-400s.

“It’s not important whether unjust US sanctions are soft or harsh, sanctions in themselves are wrong.”

Turkey says its purchase of the S-400s was not a choice, but rather a necessity as it was unable to procure defense systems from any NATO ally on satisfactory terms.

The United States says the S-400s pose a threat to its F-35 fighter jets and to NATO’s broader defence systems. Turkey rejects this and says S-400s will not be integrated into NATO.

“If the United States thinks strategically, they need Turkey very much. They say this, but they must do what is necessitated by this,” he said.