Defence Secretary Mark Esper said the decision was made to prevent a bloody conflict between Turkey and US-backed Kurdish fighters that ‘gets worse by the hour’.
But Trump has already been accused of abandoning his Kurdish allies after pulling around 30 troops from the Turkish attack zone along the border, which led to Turkish forces invading northern Syria.
Fierce fighting on Sunday reached a displaced-persons camp in Ayn Issa, around 20 miles south of the Turkey-Syria border, where the Kurdish-led administration said in a statement that 950 IS supporters escaped after attacking guards and breaching the gates.
The British-based Syrian Observatory for Human Rights said Turkish warplanes hit villages in its vicinity with ‘heavy and violent rocket shelling’ as Pro-Turkish soldiers advanced.
Wives and widows of IS fighters and their children were among those fleeing the violence near the camp, it added.
The human rights monitor said some 53 civilians have been killed since the start of the operation, including a child and a female politician shot dead by pro-Turkish gunmen.
According to the United Nations (UN) more than 130,000 people have fled their homes since Wednesday.
Pentagon chief Mr Esper, who did not give a timeline of withdrawal of troops, said Trump made the decision to pull out because the US has come to believe that the Kurds are attempting to ‘cut a deal’ with the Syrian army and Russia to counter the invading Turks.
Trump, in a tweet Sunday, said: ‘Very smart not to be involved in the intense fighting along the Turkish Border, for a change.
‘Those that mistakenly got us into the Middle East Wars are still pushing to fight.
‘They have no idea what a bad decision they have made. Why are they not asking for a Declaration of War?’
Meanwhile, hundreds of demonstrators opposed to Turkey’s military assault in the north of Syria descended on Westminster earlier today.
Protesters holding placards bearing images of Turkish president Recep Tayyip Erdogan demanded the Nato member cease its air and ground offensive, which began five days ago.
It comes after Prime Minister Boris Johnson and Foreign Secretary Dominic Raab urged Mr Erdogan to halt the incursion, saying it could undermine the fight against IS jihadists and worsen the humanitarian crisis in the war-ravaged region.
Mr Erdogan said he would not negotiate and vowed to push on with carving out a 20-mile safe zone along the border.
Turkey said 440 Kurdish fighters and four of its soldiers have been killed since the operation began.
The Kurdish-led Syrian Democratic Forces said 56 of its fighters have died.
The Americans have been working for five years with a Kurd-led Syrian group known as the Syrian Democratic Forces to combat the Islamic State group.
Turkey has long objected to the US-Kurd alliance because Turkey considers elements of that force to be terrorists tied to an insurgency inside Turkey.