Turkey's president threatened to close two strategic military bases used by the United States and NATO if Washington imposes sanctions in response for Turkey's purchase of a Russia antiaircraft system.
The threat by Recep Tayyip Erdogan, made December 15 in an interview with A Haber TV, was the latest sign of worsening relations between Ankara and Washington.
"If necessary, we can close Incirlik and we can close Kurecik," Erdogan said in the interview.
The Incirlik Air Base has been a strategic facility for U.S. and NATO forces for decades. The base at Kurecik is home to a major NATO radar station.
It wasn't immediately clear how much Erdogan's threat was bluster or a genuine signal of his intentions.
Ties between Turkey and the United States have worsened since an attempted coup in 2016, which Erdogan has blamed on a Turkish businessman living in exile in the United States.
Relations worsened further when Erdogan said he would move to buy an advanced S-400 missile system from Russia. Washington has said the system poses a threat to U.S. F-35 jets that use Incirlik.
And the move by Turkish armed forces to enter Syria in October, targeting U.S.-allied Kurdish forces there, has prompted vocal opposition from both Republicans and Democrats in Congress.
Last week, a U.S. Senate committee backed legislation to impose sanctions on Turkey for the S-400 missiles, and other things.
U.S. President Donald Trump's criticism of Erdogan has been largely muted, to the dismay of many U.S. lawmakers.