A view shows a new S-400 "Triumph" surface-to-air missile system after its deployment at a military base outside the town of Gvardeysk near Kaliningrad, Russia March 11, 2019. (Reuters photo)

ANKARA, June 14 (Xinhua) -- Turkey will retaliate if the United States imposes sanctions over its purchase of the Russian S-400 air defense systems, Turkish Foreign Minister Mevlut Cavusoglu said on Friday.

"If the U.S. takes any negative actions towards us, we will also take reciprocal steps. We will certainly respond," Cavusoglu said when asked about possible U.S. sanctions in an interview with Anadolu Agency.

But he didn't give the details on which measures Turkey would take against the U.S..

"We will not step back on Russian S-400 deal no matter what the consequences will be," Cavusoglu stressed.

The U.S. repeatedly warned it will cut off Turkey's purchase of F-35 fighter jets if Ankara goes ahead with plans to buy Russian S-400 air defense system, expected to be delivered as early as next month, triggering a heated dispute between the two NATO allies.

Last week Pentagon announced in a letter that it would halt F-35 fighter jet training for Turkish pilots, and all Turkish trainees in the program must leave the country by July 31.

Turkish President Recep Tayyip Erdogan insisted on Wednesday that Turkey had already bought the Russian S-400 system and it is set to take delivery in July.