Turkish President Recep Tayyip Erdogan says that Turkey will "crush the heads" of Kurdish fighters if they do not withdraw from a planned safe zone area in northern Syria.
Turkey agreed on Thursday to suspend an offensive for five days to allow the Kurds to retreat from the area.
But on Saturday both sides accused the other of violating the ceasefire.
Ankara views the Kurdish forces as terrorists and wants to create a "safe zone" buffer inside Syria.
Despite the temporary ceasefire, some sporadic violence has continued - particularly around the border town of Ras Al-Ain.