“Regarding Syria and Turkey, I’m most worried about Turkey’s connection with Russia. It is disturbing that Turkey is withdrawing from NATO’s orbit, ”Esper quoted TASS as saying.

He noted that the task is to "understand how ... to bring them back, to bring them closer to NATO."

Earlier, Turkish President Recep Tayyip Erdogan made the purchase on favorable conditions of the American Patriot anti-aircraft missile systems, which along with the Russian S-400 systems will help diversify Turkey's air defense.