If necessary, the soldiers of the additional forces can move around the country and can leave the territory of Syria from time to time, according to the CNN broadcaster.
The US officials did not disclose how much time the withdrawal would take. They also did not provide information on whether it had already started.
The news about the reinforcements comes after an explosion in the Kurdish-held city of Manbij claimed lives of at least four US troops.
READ MORE: Macron: France to Keep Military Presence in Syria-Iraq Region Over Next Year
In December, US President Donald Trump claimed that the US forces would pull out of Syria since the Daesh* terrorist group had been defeated there. The decision led to resignations of Secretary of Defence James Mattis and US Special Envoy for the Global Coalition to defeat the Daesh Brett McGurk.
* Daesh (ISIL/ISIS/IS/Islamic State) is a terrorist organisation banned in Russia