Turkey's use of Russian S-400 'incompatible' with role as US, NATO ally, says State Department
Turkish President Recep Tayyip Erdogan has a direct line to US President Donald Trump and has gotten adept at using it, knowing he can always go over the head of lower-level US officials issuing warnings or expressing concerns over Turkey’s conduct, such as the Turkish military’s testing of the Russian S-400 missile defense system last week.