Another defence official told the CNN broadcaster that the order had been signed by outgoing US Defence Secretary James Mattis.
READ MORE: Macron Voices Deep Regret Over US Decision to Withdraw Troops From Syria
The order clarifies how and when the withdrawal of US troops from Syria will take place, but the source refused to give any further details on the matter, according to the TV channel.
Mattis announced his resignation on Thursday, a day after US President Donald Trump decided to withdraw US troops from Syria, saying on Twitter that the United States had defeated the Daesh* terrorist group in the Middle Eastern country.
*Daesh (also known as ISIS/ISIL/IS) is a terrorist group banned in Russia