The only concern the United States has about the decision of its NATO ally Turkey to buy Russian S-400 air defence systems is that of interoperability, US Department of Defense spokesperson Capt. Jeff Davis said in a briefing on Monday, Sputnik reported.
"Our only concern about it is one of interoperability... but it is a Turkish decision," Davis told reporters.
On Friday, Turkish presidential spokesman Ibrahim Kalın said only a few nominal issues are left to clear up in a generally formalized contract on the delivery of Russia's S-400s to Turkey.
Turkish President Recep Tayyip Erdoğan said last week that Ankara and Moscow had signed a document on supplies of the S-400 Triumf systems.
