President Donald Trump last month claimed the Daesh terrorist group had been defeated in Syria and said all US troops were "coming back now," AFP reported.
But in the weeks since he gave the order, and the Pentagon began to implement it, Trump himself and members of his administration have delivered mixed messages about when a troop withdrawal may actually occur.
Trump's National Security Advisor John Bolton last Sunday announced conditions for a withdrawal that appeared to delay it indefinitely.
Adding to the confusion, a military spokesman said the US had already begun "the process of our deliberate withdrawal" from Syria.
Late Friday, Pentagon spokesman Cmdr. Sean Robertson said that Operation Inherent Resolve "is implementing the orderly withdrawal of forces from northeast Syria within a framework coordinated across the US government."
The withdrawal, Robertson said, "is based on operational conditions on the ground, including conversation with our allies and partners, and is not be subject to an arbitrary timeline."
He added, "For purposes of operational security, we will not discuss specific troop movements or timelines.
"However, we will confirm that there has been no redeployment of military personnel from Syria to date. The mission has not changed."
US defense officials said the withdrawal was only of certain types of gear, and not troops.
"We are not withdrawing troops at this stage," one US defense official said.
A second US defense official told AFP that the military had conducted a number of preparations for a deliberate withdrawal.
"That includes planning for the moving of people and equipment, preparation of facilities to accept retrograde equipment," the official said, noting that no troops had been withdrawn.
The so-called Syrian Observatory for Human Rights reported earlier that the US-led coalition in Syria had started scaling down its presence at Rmeilan airfield in the Hasakah province of northeastern Syria.
But the first defense official said this was merely part of a regular troop movement.
The US-led coalition has several other bases across northeastern Syria, as well as in neighboring Iraq, where Trump has said American forces will remain.
The coalition, which also includes countries such as France and Britain, was formed in mid-2014 apparently to counter Daesh, which had seized swathes of Iraq and Syria and proclaimed a "caliphate."
The start of the drawdown coincided with a Middle East tour by US Secretary of State Mike Pompeo, who insisted in Cairo on Thursday that the withdrawal would go ahead despite widespread criticism.