The Pentagon says it will bolster the U.S. military presence in a northeastern region of Syria to prevent potentially resurgent Islamic State (IS) extremists from seizing the oil fields.
The decision on October 24 comes days after President Donald Trump announced a withdrawal of U.S. troops from along the Turkish border area to allow Turkish forces to set up a so-called "safe zone" free of U.S.-allied Syrian Kurdish fighters.
Turkish and Russian forces are now set to patrol the area near the border that formerly was held by U.S. forces and allied Kurdish militias. An AFP correspondent saw a Russian patrol set off from Qamishli westward along the border flying Russian flags.
Trump's decision was blasted by both Democratic and Republican lawmakers and others, with many raising fears that some of the estimated 10,000 IS prisoners being held by the Kurdish-led Syrian Democratic Forces (SDF) could escape during the turmoil.
"One of the most significant gains by the U.S. and our partners in the fight against ISIS was gaining control of oil fields in eastern Syria -- a crucial source of revenue for ISIS," a defense official said in a statement on October 24, using an alternate acronym for IS.
"The U.S. is committed to reinforcing our position, in coordination with our SDF partners, in northeast Syria with additional military assets to prevent those oil fields from falling back into the hands of ISIS or other destabilizing actors," the statement said.
"We must deny ISIS this revenue stream to ensure there's no resurgence," it added.
Following his comments of a pullout of U.S. forces, Trump on October 23 said a few troops would stay behind to protect oil fields.
"We have secured the oil and, therefore, a small number of U.S. troops will remain in the area where they have the oil," said Trump, who suggested a figure of between 200-300 troops.
The Pentagon's latest remarks did not specify a number of troops or the exact location of their intended base of operation, but it appeared to be a reference to oil fields in Deir el-Zour Province of Syria.
Defense Secretary Mark Esper has said the main goal of a continued U.S. troop presence would be to ensure that IS fighters are contained and unable to gain control of the oil fields and the revenue they generate.
Syria's oil industry has largely been left in ruin, although some operations still exist in the eastern part of the country and have been a key source of revenue for the Kurdish-led administration there.
The Kurds seized control of the more profitable oil fields in Deir el-Zour Province after driving out IS militants in 2018.