He added: "For purposes of operational security, we will not discuss specific troop movements or timelines".
The removal of the equipment in recent days was first reported by CNN, which quoted an administration official with direct knowledge of the operation as saying it signaled the beginning of U.S. withdrawal from the Middle Eastern country.
"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equipment, preparation of facilities to accept retrograde equipment", the official said, noting that no troops had been withdrawn.
But the USA pullout risks leaving the Kurds at the mercy of Turkey, which views the fighters as terrorists.
Top U.S. officials were shocked too, including Defense Secretary Jim Mattis, who quit in protest.
The Syrian Observatory for Human Rights activist group reported that the coalition had started scaling down its presence at Rmeilan airfield in the northeastern province of Hasakeh.
There has been confusion over plans to implement Trump's pullout order and threats from Turkey to attack the Kurdish fighters, who Ankara views as terrorists due to their ties to insurgents within Turkey.
President Trump announced that the U.S. would withdraw its estimated 2,000 United States troops from Syria on December 19, saying their mission of defeating Daesh (ISIS)* had been completed and that bringing USA military personnel home from wars in the Middle East would fulfil a campaign promise. Brett McGurk, the president's special envoy for the USA coalition in Syria, and Dana White, a Defence Department spokeswoman, also resigned.
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The case has been kept quiet by the media over the past 10 weeks over fears that coverage could cause harm to the missing woman. He is the majority owner in Elkraft-an electricity company he co-founded in 1992-holding 70 percent of the firm.
Turkey considers America's Kurdish allies of the YPG militia - who were vital in the ground war against ISIS - a terrorist group. The anti-ISIS coalition has sought to quell violence between the Kurds and Turkish forces, which has at times drawn the SDF away from fighting ISIS militants. Turkish President Recep Tayyip Erdogan then canceled a planned meeting with Bolton.
Trump initially seemed to call for an immediate withdrawal but has since suggested the pullout would be more gradual.
His statements appeared to contradict those made earlier by Trump.
Baghdad declared victory over ISIS in late 2017 but has continued to battle the group with US help as the extremist fighters have shifted to conducting an insurgency.
Trump administration officials also have argued that the US needs to stay in Syria to counter Iran's presence there.
"We remain committed to the complete dismantling of ISIS - the ISIS threat - and the ongoing fight against radical Islamism", he said.
In his speech at the American University in Cairo on Thursday, the secretary of state said the U.S. would continue working with coalition partners to defeat ISIS and would continue air strikes against terrorist targets in the region.
U.S. Secretary of State Mike Pompeo, who has been touring the Middle East this week to reassure allies of Washington's commitment to regional security, said on Thursday the withdrawal would not be scuppered despite the Turkish threats.