"We are ready to cooperate with the Turkish colleagues in this area, but I don’t want to dwell on some specific things now. There is readiness, in fact, and then we’ll see," he said.

Asked about whether Ankara is concerned about the possible introduction of sanctions for cooperation with Moscow in this sphere, the diplomat noted that the sphere of military-technical cooperation "does not like publicity." "The one thing I can say is: we should assume that Turkey is a sovereign and independent state which has the full right to develop cooperation with the states it chooses," Yerkhov stressed.

In November 2016, it emerged that Turkey and Russia were negotiating the purchase of S-400 anti-aircraft missile systems. The Russian side confirmed the conclusion of the contracts on September 12, 2017, whereas Turkish President Tayyip Erdogan reported that Turkey had already paid an advance on the contract. Turkey will become the first NATO member state to receive S-400s from Russia. The number of supplied systems was not officially specified.

US Assistant Secretary of State for European and Eurasian Affairs Wess Mitchell warned on June 26 that the purchase of S-400s by Turkey will lead to the introduction of sanctions against Ankara by Washington and drastic changes in bilateral relations. In addition, the US may refuse to transfer the purchased F-35 planes to Turkey.