NATO concerned over consequences of Turkey's purchase of Russian S-400

NATO Secretary General Jens Stoltenberg (L) and Turkish Foreign Minister Mevlut Cavusoglu attend a press conference in Ankara, Turkey, on May 6, 2019. NATO Secretary General Jens Stoltenberg said on Monday that he is worried about Turkey's plans to deploy the Russian S-400 missile defense system despite of U.S. objection. (Xinhua/Mustafa Kaya)