This undated file picture shows highly advanced Russian-built S-400 air defense systems at an unknown location in Russia...

This file picture shows a Russian-made S-400 air defense missile system in an undisclosed location in Russia...

This photo released by the Turkish Air Force shows a transport aircraft unloading medical supplies at Andrews Air Force Base, Washington, US on April 28, 2020...

A handout picture taken and released on August 27, 2019, by the Turkish Defense Ministry shows a Russian military cargo plane, carrying S-400 missile defense system from Russia...

This file picture shows Russian-built S-400 missile defense systems deployed in an undisclosed location in Russia...

Russia says it has started the production of a batch of S-400 missile defense systems for India under a deal the two countries reached two years ago, despite threats of sanctions made by the United States against New Delhi over the purchase of the advanced Russian systems...

Turkey has condemned as “unacceptably threatening” a US House of Representatives resolution that slammed Ankara’s purchase of advanced Russian-built S-400 air defense missile systems and urged sanctions on Washington’s NATO ally over the acquisition of the military hardware...

The United States says it has no plans for the time being to accept any additional Turkish pilots to train on F-35 fighter jets as part of a planned program between the two countries...

Turkish President Recep Tayyip Erdogan has reaffirmed his country’s commitment to an agreement with Moscow to buy Russian S-400 missile defense systems, saying Ankara will not step back from the deal despite US threats of “devastating” consequences...

Turkish President Recep Tayyip Erdogan says his country is seeking to acquire the Russian S-500 missile defense system, a more advanced version of the S-400, taking a dispute with the United States up a notch...

Turkish President Recep Tayyip Erdogan has criticized the United States for threatening to stall the delivery of F-35 fighter jets to his country over the purchase of Russian-built advanced S-400 air defense missile systems, complaining that Ankara is being subjected to “an imposition” and unfair treatment on the issue...

The United States has stopped shipment of equipment for F-35 equipment to Turkey over the country’s defensive cooperation with Russia, a report says...