A spokesperson for the US -led coalition against the Islamic State militant group (ISIS) said the withdrawal had gone ahead despite mixed messages from the White House over the fate of the 2,000 troops operating in the country.
Very complicated: Bolduc, who served in the Pentagon during the USA troop withdrawal from Iraq in 2011, said the logistical challenge of getting out of Syria will be less taxing, but the Pentagon still must discern important questions - such as the size of the pullout, and the weapons and equipment that will be turned over.
The Syrian Observatory for Human Rights reports that the withdrawal began late Thursday.
It said a convoy of ten armoured vehicles and some trucks had pulled out of Rmeilan, in Syria's north west, into Iraq.
President Donald Trump's announcement last month that he had made a decision to withdraw the 2,000 USA troops there stunned allies who have joined Washington in the battle against ISIS militants in Syria.
Following the announcement, Defense Secretary James Mattis submitted his resignation letter.
A USA official told ABC News that in recent days military equipment has been moved out of Syria into Iraq.
Pompeo arrived in Abu Dhabi on Friday as part of his regional tour aimed at reassuring Washington's Middle Eastern allies of its continued commitment to the complete dismantlement of Daesh a href="https://sputniknews.com/us/201812191070826973-us-military-syria/" *withdraw some 2,000 U.S. troops now deployed in the Middle Eastern country.
In a Sunday-night tweet, Trump said his government was starting the "long overdue pullout" from Syria while hitting the "little remaining" Islamic State "territorial caliphate" and would attack again from a nearby existing base if the jihadist group regroups.More news: Hotstar removes KWK's Hardik Pandya-KL Rahul episode after the huge controversy
More news: Kimmel 'Hires' Federal Employees to Work on Show During Shutdown
More news: US, China leave future of trade talks unclear
"It doesn't materially alter our capacity to continue to perform the military actions that we need to perform", Pompeo told reporters in Abu Dhabi.
While the USA military pullout is now officially underway it has made a slow start.
USA troops have been involved in the Syrian conflict since 2014.
19 announcement that he was moving to disentangle USA troops from Syria's complex battlefield sparked fears that the move might undo efforts to defeat the Islamic State's final remnant in Syria.
USA forces' vehicles and structures are seen on the outskirts of the northern Syrian town of Manbij on December 26, 2018. Following the announcement, he was forced to reiterate the U.S.'s commitment to its more substantial troop to neighboring Iraq, where the US -led coalition is also fighting ISIS.
On an unannounced visit to troops stationed near the Syrian border Friday morning, Turkey's defense minister Hulusi Akar reiterated Ankara is "determined" to fight Kurdish militias it considers terrorists and said military preparations were ongoing.
Foreign Minister Mevlut Cavusoglu went so far on Wednesday as to say that if the USA withdrawal from Syria was delayed, "then we will put this decision into practice", suggesting Turkey could go after the Kurds in short order.
"When the time and place comes, the terrorists here will also be buried in the ditches and trenches they have dug", the minister said in southern Sanliurfa province.
Earlier this week, Bolton called security assurances for the US -backed Kurdish forces a necessary condition for the withdrawal of USA forces from Syria.
But Bolton also said the United States was still seeking some guarantees of that agreement through "protocols and procedures".