"CJTF-OIR has begun the process of our deliberate withdrawal from Syria", spokesman Colonel Sean Ryan told the AFP news agency in a statement, referring to the US-led anti-Islamic State group (IS) force. A convoy of about 10 armored vehicles and some trucks pulled out of Rmeilan, Syria, heading for and into Iraq.
Extending the timeline further, national security adviser John Bolton said on Sunday that the pullout was conditional on the defeat of the last remnants of the Islamic State and guarantees from Turkey that it would not attack Kurdish forces aligned with the United States.
US Secretary of State Mike Pompeo insisted on Thursday that US troops will leave Syria, ahead of a keynote speech aiming to lay out a coherent US policy in the Middle East.
"This is the first such pullout of American forces since the USA president's announcement" of a full troop withdrawal from Syria last month, he said. On Friday, he told Egyptian state TV that the USA will pull out of Syria as the president ordered, "but we'll do so in a way that makes sense, that is orderly, that does everything we can to ensure the security of those who fought alongside us defeating the caliphate inside of Syria".
US President Donald Trump's "decision to withdraw our troops has been made".
"These have been folks that have fought with us and it's important that we do everything we can to ensure that those folks that fought with us are protected", Pompeo said of the Kurds while visiting Erbil, the capital of Iraq's semi-autonomous Kurdistan region, after talks in Baghdad.
Speaking to reporters in Moscow Friday, she said it appears to Moscow that the U.S.
There were no other details, and it was not immediately clear how many vehicles or whether any troop units had withdrawn.
Turkey considers America's Kurdish allies of the YPG militia - who were vital in the ground war against ISIS - a terrorist group.
Meanwhile, Turkey's defense minister Hulusi Akar said on Friday that his country is preparing for an "intense" attack across the Euphrates in Syria, as soon as the Americans withdraw.
However, Turkish Foreign Minister Mevlut Cavusoglu said the Turkish offensive would go ahead whether USA troops were in the area or not.
Ankara's anger over preconditions announced by Bolton before any US withdrawal, including security guarantees for the Kurdish militia, may have brought forward the timing of a strike against the YPG. He suggested that the protection of Kurdish allies in the country would be a redline for the withdrawal. If not, the Trump administration would be accused of abandoning an ally to a grim fate.