The base is used to launch attacks against ISIS.
The U.S. says its working to resume air operations against ISIS from the base.
Washington also cautioned Americans against traveling to the region.
Washington's increasing coziness with the Syrian Kurds has made Turkey nervous.
"Islamic State poses the biggest threat to Turkey both because it is right on the other side of our border and also due to the flow of foreign fighters."
A major shift in stance is reported after clashes on Turkey's Syria border.