Confirmation of the first withdrawals comes amid confusion over plans to implement Trump's pullout order and threats from Turkey to attack Kurdish fighters, who have been America's partners on the ground in the war against the Islamic State group in Syria.
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.
FILE - In this Wednesday, April 4, 2018 file photo, a USA soldier, left, sits on an armored vehicle behind a sand barrier at a newly installed position near the front line between the U.S-backed Syrian Manbij Military Council and the Turkish-backed fighters, in Manbij, north Syria.
The U.S. -backed Syrian Kurdish People's Protection Units form the backbone of the opposition Syrian Democratic Forces and have been fighting alongside U.S. troops against Islamic State militants in northeastern Turkey.
The CNN report added that officials it had previously spoken to said the Pentagon wants to signal to the president it is working towards his goals following his withdrawal decision last month.
This is a developing story.
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Global players in the conflict have been in talks about the future of former US territory in Syria.
The news that a withdrawal had begun was confirmed on Thursday by the Syrian Observatory for Human Rights, based in the United Kingdom, which monitors activity in the war-town country through a network of activists.
American officials wanted to condition a U.S. troop withdrawal on a guarantee of safety for its Kurdish allies and a Turkish commitment to non-aggression, an idea President Erdogan hated so much, he refused to meet with NSA John Bolton who had flown all the way to Ankara to meet with him.
"Although we made a clear agreement with U.S. President Trump, different voices are emerging from different parts of the administration", Erdogan said this week as Bolton wrapped up his visit. Trump's abrupt decision in December to pull them, declaring in a tweet the defeat of ISIS, sent shockwaves across the region and led to the resignation of U.S. Defence Minister James Mattis and the top U.S. envoy to the anti-ISIS coalition. Ankara views U.S. Kurdish allies the YPG in Syria as one and the same with the PKK, a group that has waged a 34-year insurgency against Turkey. The lira fell sharply Tuesday on fears of renewed U.S. On Thursday, Pompeo declared that the U.S.is a "force for good" in the Middle East. On Dec. 23, he said there would be a "slow & highly coordinated pullout of US troops from the area".
A US military official spoke Friday of the withdrawal process, but declined to comment on specific timetables or movements.
Bolton's comments angered Erdogan, who abruptly canceled a planned meeting earlier this week.