U.S. Defense Secretary Mark Esper said he wants an explanation from Ankara over threats to close the Incirlik airbase for the United States.
Esper said he would need to speak to his Turkish counterpart, defense minister Hulusi Akar, "to understand what they really mean and how serious they are."
"If the Turks are serious about this, I mean, they are a sovereign nation to begin with... they have the inherent right to house or not to house NATO bases or foreign troops," the AFP cited him as saying.
"I think this becomes an Alliance's matter, their commitment to the Alliance, if indeed they are serious about what they are saying," the Pentagon chief added.
Earlier, Turkey's President Recep Tayyip Erdogan threatened to close the Incirlik and Kurecik bases, if sanctions are imposed against Ankara.