Turkish Defence Minister Hulusi Akar has disclosed some details regarding the future of Russian-made S-400 air defense system purchase.

According to Turkey’s state-owned Anadolu news agency, quoting Turkish Defence Minister Hulusi Akar, the delivery and installation of the S-400 system were will begin in October 2019.

Turkish Defense Minister also said that personnel would be sent to Russia to receive training at the start of 2019, according to Hurriyet. He said the F-35 fighter jet program with the United States was continuing as planned, with the third and fourth jets in the program to be delivered in March next year.

Turkey’s purchase of the S-400 systems, which are not compatible with NATO defenses, has unnerved the United States and NATO member countries, which are already wary of Russia’s presence in the Middle East.

Washington and NATO officials strive to prevent the sophisticated Russian-built anti-aircraft weapon system from collecting information about the US-made all-weather stealth multirole warplanes, technically known as the Lockheed Martin F-35 fighters, just as they are gaining a foothold in Europe.

According to Der Spiegel, for NATO, the supply of Russian anti-aircraft missile systems S-400 to Turkey is a real provocation. Within NATO, resistance is mounting.

The purchase of the S-400 planned by Turkey means “a lot of trouble,” US Secretary of Defense James Mattis said in Congress.

In recent years, tensions between Ankara and other NATO alliance members, particularly Washington, have escalated amid an array of political differences, such as US support for the Kurdish People’s Protection Units (YPG), which Ankara sees as an extension of the Kurdistan Workers’ Party (PKK), a terrorist group banned in Turkey.