ANKARA (Reuters) - Turkey will not turn back on its purchase of Russian S-400 missile defence systems and will take reciprocal steps after evaluating U.S. sanctions imposed over the acquisition, Foreign Minister Mevlut Cavusoglu said on Thursday.

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

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

In an interview with broadcaster Kanal 24, 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 the 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 defence 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.

The sanctions come at a delicate moment in fraught relations between Ankara and Washington as Democratic President-elect Joe Biden gears up to take office on Jan. 20, replacing Republican incumbent Donald Trump.

Asked whether ties could normalise under Biden, Cavusoglu said that depended on whether Washington would meet Turkish expectations on Syria policy and the extradition of a U.S.-based cleric Turkey accuses of orchestrating a 2016 coup attempt.

“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.