Turkey's President Recep Tayyip Erdogan on Sunday threatened to close two strategic military bases used by the US after Washington warned of sanctions over the buying of Russian arms.
"If necessary, we can close Incirlik and we can close Kurecik," Mr Erdogan said on the pro-government A Haber television channel.
Mr Erdogan has regularly raised this possibility in the past, at times of tension between the two countries.
The US Air Force uses the airbase at Incirlik for raids on positions held by ISIS in Syria. The Kurecik base houses a major Nato radar station.
Foreign Minister Mevlut Cavusoglu raised the issue of the bases last week. Responding to Washington's threat of new sanctions, he warned that their closure could be "put on the table".
Turkey faces sanctions over its decision to buy the Russian S-400 missile defence system, despite warnings from Washington.
Also on Sunday, Mr Erdogan held talks with the head of UN-backed Government of National Accord in Libya, Fayez Al Sarraj, in Istanbul. The meeting came days after the Turkish leader said he was ready to send troops into Libya if it was requested by Mr Al Sarraj's administration.
The closed-door meeting, which was not on Mr Erdogan's official agenda, took place in Istanbul's Ottoman-era Dolmabahce Palace, the Turkish presidency said without giving details.
During the previous meeting between the two men, in Istanbul on November 27, the two agreed a deal on security and military co-operation, as well as maritime jurisdiction.
The deal came despite calls from the Arab League — which includes Libya — to end co-operation with Turkey in protest at its military offensive against Kurdish forces in Syria.
Libya has been mired in chaos since a Nato-backed uprising that toppled dictator Muammar Qaddafi in 2011.
And on Friday, Turkey summoned the US ambassador after the Senate followed the lower house and voted to recognise the 1915 killings of Armenians as genocide. The bill has yet to be signed by President Donald Trump.
Armenia says 1.5 million people died in the killings. Turkey says the number of deaths was far lower and Turks also died.
