Turkey tested Russia’s S-400 missile defence system on U.S. fighter jets in November 2019, Russian state-run TASS news agency reported on Wednesday, citing an unnamed source close to the Turkish defence industry.

"Yes, such trials have indeed taken place last November," the source told TASS when asked to comment on media reports on the subject dating from November. 

On November 25, 2019, CNN Türk reported that various aircraft, including F-16 fighter jets, were scrambled near Ankara to test the S-400 system. The Turkish military reportedly tested communication between the air defence systems and the aircraft during those exercises.

On Nov. 29, video footage by Turkey’s TRT channel, featuring Russia’s S-400 systems and U.S.-made F-16 and F-4 aircraft, was posted to YouTube.

Russia said in September 2017 that it had signed a $2.5 billion contract for supplies of its S-400 missile systems with Turkey. The first batch was delivered to Ankara in July 2019, in spite of protestations from NATO that it would undermine its own defence systems. 

The United States formally expelled Turkey from NATO’s F-35 fighter jet programme over the purchase of the the S-400 system in July 2019, although Turkish manufacturers are still supplying parts.

The TASS report coincided with a bipartisan letter sent by U.S. lawmakers to U.S. Defence Secretary Mark Esper on Monday urging the Pentagon to stop buying F-35 fighter jet components from Turkey as it undercuts U.S. pressure on the country over its purchase of the Russian S-400 defence system.