Duvar English/Reuters

Turkish F-16 warplanes started flying over the country’s capital Ankara on Nov. 25 to test its new Russian S-400 missile defenses despite pressure from Washington for Turkey to drop the system.

The statement released from the Ankara Governor’s Office said that F-16 fighter jets will fly over Ankara on Nov. 25 and Nov. 26 as part of “some projects carried out in coordination with the Presidency of Defense Industries.”

It also said that the F-16s and other aircraft will conduct low- and high-altitude flights over the capital to test an air defense system project.

Ankara’s purchase of the S-400s has been a major factor souring relations with the United States, which says the system is not compatible with NATO defenses and poses a threat to Lockheed Martin’s F-35 stealth fighter jets.

Dealers said the reports had a negative impact on the lira, which weakened to 5.7380 against the dollar from a close of 5.7140 on Nov. 22. Tensions in U.S.-Turkish relations played a major role in a near 30 percent slide in the lira’s value last year.

Ankara began receiving the S-400s last July but they are not yet operational.

Last week, a senior State Department official told reporters Turkey needed to “get rid of” the system. Those comments came after President Recep Tayyip Erdoğan met U.S. President Donald Trump at the White House.

Trump said their talks were “wonderful” but it was unclear if the two NATO allies made any breakthrough on the S-400 issue and Erdoğan subsequently said U.S. pressure to get rid of the S-400s was an infringement of sovereign rights.

Washington has suspended Turkey from the F-35 program, which it was a buyer and producer of, to punish it for the S-400 purchase. It has warned of possible U.S. sanctions over the deal but has not yet imposed them.

Trump has told Erdoğan the United States is ready to sell Ankara U.S. Patriot systems if it drops the Russian system.