The official quoted by CNN would not describe exactly what the cargo was or how it was being transported.
The Pentagon first gave word of the start of the withdrawal late Thursday.
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. "Out of concern for operational security, we will not discuss specific timelines, locations or troop movements", Colonel Sean Ryan said.
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. Turkey, however, considers the YPG a terrorist group linked to a rebellion in Turkey. Recent reports have indicated the USA is considering leaving some troops in place at the al-Tanf base in southern Syria, which is seen as a key bulwark against Iran. He said military preparations were ongoing.
The reports could not be independently confirmed.
The statement coming a day after U.S. Secretary of State Mike Pompeo in Cairo defended the withdrawal, insisting it was not a retreat.
USA forces have "begun the process of our deliberate withdrawal from Syria", Col. Sean Ryan, the spokesman for the US -led coalition against the Islamic State said.
Mr Trump also said that Russia, Iran and Syria had been the biggest beneficiaries of United States action in Syria and it was time to bring American soldiers home. "That framework is conditions-based and will not subject troop withdrawal to an arbitrary timeline".
Many are also anxious that the Kurdish forces, which spearheaded the fight against the "Islamic State" militants with U.S. backing, would be left vulnerable to an imminent attack by Turkey.
Turkey views the US-backed YPG Syrian Kurdish militia as an extension of the Kurdistan Workers' Party (PKK), which has waged a 34-year insurgency in Turkey for Kurdish political and cultural rights, mostly in southeastern areas near Syria.
U.S. Secretary of State Mike Pompeo, holds a joint press conference with Qatari Foreign Minister Sheikh Mohammed bin Abdulrahman Al Thani, at the Sheraton Grand in Doha, Qatar, Sunday, Jan. 13, 2019.
Turkey's Defense Minister Hulusi Akar reviews an honor guard as he arrives for a meeting with the commanders of military units on Syrian border in Sanliurfa, southeastern Turkey, Jan. 11, 2019.
She also confessed that the terrorist organization forcefully recruited underage children and sent them to fight against Turkish soldiers during the Operation Olive Branch.
Earlier this week, Bolton called security assurances for the USA -backed Kurdish forces a necessary condition for the withdrawal of US forces from Syria.
"We recognize the Turkish people's right and President Erdogan's right to defend their country from terrorists and we also know that those who aren't terrorists, those who were fighting alongside us all this time, deserve to be protected and we are confident that we can achieve an outcome that achieves both of those: protect the Turks from legitimate terror threats and prevent any substantial risks to folks who don't present terror risks to Turkey", Pompeo told reporters.
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