Mr Trump tweeted on Sunday that the withdrawal from Syria had begun, and that the US would “devastate Turkey economically if they hit the Kurds”.
He also said any remaining IS fighters could be attacked from the air, and that a 20-mile (32km) “safe zone” could be established.
Turkey has dismissed President Donald Trump’s threat to “devastate” its economy if it attacks Kurdish forces in Syria following a planned pullout of US troops.
“You cannot get anywhere by threatening Turkey economically,” Foreign Minister Nevlut Cavusoglu said.
US forces have fought alongside a Kurdish militia in northern Syria against the Islamic State (IS) group.
Turkey, however, regards the People’s Protection Units (YPG) as terrorists.S
In December Mr Trump announced that the US would pull out all troops from Syria because the Islamic State militant group had been “defeated”.
The sudden move shocked allies and led to criticism. Several senior US military officials resigned shortly afterwards.
There were also fears that Kurds in the Syrian Democratic Forces (SDF), which had partnered with the US, would be attacked by Turkey once the US withdrew.