The new warning came on Thursday from US State Department spokesperson Heather Nauert, who said that Washington has "serious concerns about Turkey's potential acquisition" of the S-400 anti-aircraft systems.
"Under NATO and under the NATO agreement, which of course, Turkey is a NATO member, you're only supposed to buy, they are only supposed to buy, weapons and other materiel that are interoperable with other NATO partners. We don't see that as being interoperable," the State Department spokeswoman said during a press briefing.The hotly discussed Turkey-Russia deal may signal closer relations between both nations, as well as a growing rift between Ankara and its NATO allies, mainly the US.













Comment: Turkey vies for attention between two superpowers that calculate it as strategic, but neither trusts Ankara's meandering loyalty.