The United States Department of Defence called on Turkey to take action and remove Russian S-400 missiles from its territory, reiterating the security threat to NATO defence systems in the country.
On Tuesday, the press secretary John F. Kirby said: "We urge Turkey not to move ahead with the delivery of the S-400."
"We believe it's incompatible with the F-35 [jets], and Turkey remains suspended from that program. Again, we urge them not to retain it," he continued.
The US removed Turkey from the F-35 jet global partnership programme in July 2019 after Ankara purchased Russia's S-400 air defence system, setting a course which severely damaged relations between the NATO allies.
Last week, Turkey's defence industry hired one of the United States' most prestigious law firms in efforts to re-enter the F-35 fighter jet programme.