“The issue of announced Turkish purchase of S-400 from Russia [is] something that has been the issue the US officials have been discussing intensely,” he said. “The real challenge for us [is that] we see the S-400 as threat to integrated information systems. Turkey signed up as a part of co-production arrangement to buy S-400. Our leading military officials made clear [the] country cannot have both S-400 and F-35. US has made its position very [clear] and Turkey has made its position very clear.”
“We continue to have discussions with our ally Turkey, because we are allies in NATO, about the challenges that are posed by advanced system of S-400,” he added. “But Turks themselves have suggested that any scenarios about sending S-400 to third countries are unfounded. It is a serious issue that Turkey and the US so far have not agreed. But we will continue to discuss this issue.”
On April 11, Turkish Foreign Minister Mevlut Cavusoglu said that specialists from the US and NATO could come to Turkey to make sure that Russian S-400 air defense systems do not pose a threat to NATO. He noted that Turkey is in dire need of the S-400 air defense system.
"Although the US urges Turkey to abandon the purchase of Russian S-400 air defense missile systems, it does not guarantee that it will sell us Patriot air defense systems," Mevlut Cavusoglu said.
Meanwhile, US Secretary of State Michael Pompeo stated that the US believes that Turkey would not be able to have both US F-35 fighter-bombers and Russian S-400 anti-aircraft missile systems at the same time, as this is technically impossible. “According to Pentagon sources, it is not possible to launch the F-35 in the space where the S-400 is operated,” he said.
Initial reports of negotiations between Russia and Turkey on the supply of S-400 surfaced in November 2016. The signing of a contract was confirmed by the Russian side on September 12, 2017. Turkish National Defense Minister Hulusi Akar said that the S-400 air defense systems would be deployed from October 2019. The supply of the S-400 air defense systems to Ankara cost $2.5 billion, head of the Rostec state corporation Sergey Chemezov said in December 2017. Turkey is the first country, a NATO member to receive the S-400 air defense systems from Russia.