Russian army S-400 Triumph medium-range and long-range surface-to-air missile system rehearse before the World War II anniversary in Moscow, on May 7, 2017. (Reuters File photo)

ANKARA, April 3 (Xinhua) -- Turkish Foreign Minister Mevlut Cavusoglu said on Wednesday that his country will not step back from the deal to buy the S-400 missile defense system from Russia, state-run Anadolu Agency reported.

"The S-400 deal is a done deal and we will not step back from this," Cavusoglu said at a think-tank forum in Washington, where NATO foreign ministers gathered for the 70th anniversary of the founding of the security bloc.

The Pentagon said on Monday that it had halted delivery of F-35 related parts to Turkey because of the latter's purchase of the S-400 defense system from Russia.

"We don't see our relations with Russia as an alternative to our relations with others. And nobody, neither the West nor Russia, can ask us to choose between," Cavusoglu said.

Responding to the remarks that the S-400 cannot integrate into the NATO system, the Turkish minister said the United States could establish a technical working group to ensure that the S-400 will not be a threat to F-35s or the other NATO systems.

In December 2017, Turkey finalized a deal with Russia over the purchase of the S-400 surface-to-air missile system. Russia will deliver the first batch of the defense batteries in late 2019.

Meanwhile, Turkey plans to purchase 100 F-35 fighter jets from the United States, and its pilots are training on the weapons platform at Luke Air Force Base in Arizona of the United States.