Turkey has begun bolstering its military presence on both sides of its border with Syria, just days after U.S. President Donald Trump announced he would withdraw all 2,000 U.S. troops currently based in Syria.

The move comes as Turkish President Recep Tayyip Erdogan spoke with Trump by telephone on December 23, with the two leaders agreeing on military and diplomatic coordination to prevent a power vacuum forming as the U.S. pulls out.

Reuters said an eyewitness saw hundreds of Turkish military vehicles moving into the southern border province of Kilis from neighboring Hatay Province.

Turkey's IHA news agency reported that a convoy of Turkish forces crossed into Syria during the night of December 22-23.

The Turkish military has not commented on the troop movements.

In a post on Twitter, Trump said he and Erdogan had discussed "the slow & highly coordinated pullout of US troops from the area."

U.S. troops have been in Syria working with a Kurdish militia to fight the Islamic State terrorist organization. Turkey views the militia as a "terrorist offshoot" of Kurdish militants waging an insurgency inside of Turkey.

Based on reporting by AP, Reuters, and dpa