The first reports about the talks between Russia and Turkey on the deliveries of S-400 air defense missile systems emerged in November 2016. Russia confirmed in September 2017 that the relevant contract worth $2.5 billion had been signed. Under the contract, Ankara will get a regiment set of S-400 air defense missile systems (two battalions). The deal also envisages partial transfer of production technology to the Turkish side.

"We are completing the first stage of the deliveries this week," the defense official said, stressing that the number of "those wishing to buy S-400s has not decreased."

MOSCOW, July 23. /TASS/. Russia will complete the first stage of delivering S-400 surface-to-air missile systems to Turkey this week, Head of Russia’s Federal Service for Military and Technical Cooperation Dmitry Shugayev said on Tuesday.

Turkey is the first NATO member state to purchase such air-defense missile systems from Russia. The deliveries of S-400 air defense systems to Turkey began on July 12, 2019.

The United States and NATO have been making attempts to prevent Turkey from purchasing Russia's S-400 missile systems. Washington has warned on many occasions that it may impose sanctions on Turkey, if Ankara presses ahead with the S-400 deal.

Turkey has ordered 30 out of planned 100 F-35 fighter jets from the United States. The F-35 is a fifth-generation multirole fighter jet designed using the stealth technology and is capable of carrying nuclear weapons. By now, eight countries have taken part in the project of developing the F-35 alongside the United States: Australia, the United Kingdom, Denmark, Italy, Canada, the Netherlands, Norway and Turkey. Also, Israel and Japan are purchasing these fighters.

The US White House announced on July 17 it was removing Turkey from the program of the F-35 production. The Pentagon specified that this move was not part of sanctions that could be imposed in addition to the decision on the F-35s.

The S-400 ‘Triumf’ is the most advanced long-range air defense missile system that went into service in Russia in 2007. It is designed to destroy aircraft, cruise and ballistic missiles, including medium-range missiles, and can also be used against ground installations. The S-400 can engage targets at a distance of 400 km and at an altitude of up to 30 km.