BRUSSELS (AA) Turkey’s purchase of Russian S-400 missiles is an issue concerning the bilateral relations between Turkey and the US, not NATO, said Turkey’s envoy to NATO.

“S-400 is not a NATO problem, it is a bilateral problem, the US including of NATO to this [issue] and harming the coherency of the alliance would be a mistake,” Basat Ozturk, Turkey’s permanent representative to NATO, told Anadolu Agency at the headquarters of the bloc. Ozturk said the US is expected to be in cooperation and unity in accordance with the shared values of NATO, and comply with the spirit of alliance.

Tensions between the US and Turkey have escalated in recent months with Turkey set to begin receiving the advanced S-400 Russian surface-to-air missile defense system, which Washington said will jeopardize Turkey’s role in the F-35 program and could trigger sanctions. Following protracted efforts to purchase an air defense system from the US with no success, Ankara decided in 2017 to purchase the Russian S-400.