The U.S. military has begun bolstering its troop numbers in a part of eastern Syria where President Donald Trump has said he wants to protect oil fields, U.S. defense officials said Saturday.

The U.S. troops began arriving in Deir al-Zour province in a convoy from northern Iraq. The defense officials, speaking on condition of anonymity due to the sensitivity of the issue, said the forces will reinforce American troops in coordination with the Kurdish-led Syrian Democratic Forces, who have teamed with the Pentagon on operations against the Islamic State for years.

The additional forces will help "prevent the oil fields from falling back into the hands of ISIS or other destabilizing actors," one U.S. defense official said.

"We will not discuss details or timelines of those forces for security reasons," the official added.

News photographers in the region captured photographs that show a convoy of about a dozen vehicles rolling through the Syrian city of Qamishli, many with American flags flying on them. The majority of the vehicles were mine-resistant armored vehicles, with a few civilian trucks seemingly mixed in.

The move is the latest in a whirlwind month for the Pentagon in Syria that began with Turkey telling the United States that it would launch an offensive against Kurdish parts of northern Syria. The White House announced Oct. 6 that it would not stand in the way despite years of the Pentagon partnering with Syrian Kurds on operations against the Islamic State.

Trump decided late Oct. 13 to withdraw virtually all 1,000 troops from northern Syria, but he later was convinced by other senior U.S. officials to move some back into Syria, but farther from the Syrian border with Turkey.

