"We told [the United States] that we do not respond well to threats. As of F-35, we have already signed the deal. … For June 21, there is going be a transfer for the F-35s. There is no negative development," Cavusoglu told reporters following his meeting with US Secretary of State Michael Pompeo in Washington.
On May 24, US Senate Armed Services Committee released details of its version of annual defense policy bill. The draft, in particular, implies that the delivery of US F-35 jets to Turkey should be suspended in response to Ankara's purchase of Russian S-400 anti-missile systems.
In December 2017, Russia and Turkey signed a loan agreement to supply S-400s to Ankara. The deal triggered disagreements between Ankara and Washington, with the latter threatening to impose sanctions against Turkey, as the United States believes that the weapon was incompatible with NATO defenses.