Washington will end the process of the Patriot sale if Turkey proceeds with the purchase of the Russian S-400 air defense systems, Hurriyet Daily News quoted a senior US official as saying. The US government cannot not proceed with the Patriot sale “if the S-400 sale goes forward,” the unnamed official said, citing “the congressional authorization condition.” The US is concerned that Ankara’s purchase of S-400 missiles “will endanger Turkish participation in the F-35 program and will likely result through our legislation in some sort of sanctions,” the official added. Ankara won’t strike a deal on purchasing Patriots if the US ties it with tearing up the existing arms contract with Moscow, Foreign Minister Mevlut Cavusoglu said in January.