Ankara’s purchase of Russia’s S-400 missile defense system is a done deal, Turkish Foreign Minister Mevlut Cavusoglu said on Tuesday. The statement comes despite Washington’s efforts to persuade Turkey to buy the US Patriot system instead. US and NATO officials have warned Ankara that the Russian system cannot be integrated into the NATO air and missile defense system. They also say that the S-400 system deal would jeopardize Turkey’s purchase of Lockheed Martin’s F-35 fighter jets and possibly result in US sanctions, Reuters reports.