"We have defeated ISIS in Syria, my only reason for being there during the Trump presidency," Trump said on Wednesday, referring to the armed group that once controlled vast areas of Syria and Iraq but is now confined to small pockets.
US officials said many details of the troop withdrawal had not yet been finalised, but they expect their country's forces to be out by mid-January.
Washington began air raids in Syria in 2014, a year before US ground troops moved in to fight the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) armed group and train Syrian rebels in the war-ravaged country.
Later on Wednesday, Trump suddenly declared their mission accomplished, posting a video on Twitter in which he said is "heartbreaking" to have to write letters and make calls to the loved ones of those killed in battle.
"Now it's time for our troops to come back home," said Trump, who has long stated a desire to bring soldiers based in Syria back to the United States.