WASHINGTON (Reuters) - The United States is committed to reinforcing its military position in Syria with additional assets to prevent oilfields from being taken over by remnants of the Islamic State militant group or others, a U.S. defense official said on Thursday.

FILE PHOTO: Flanked by Secretary of Defense Mark Esper (L) and Chairman of the Joint Chiefs Army Gen. Mark Milley, U.S. President Donald Trump meets with senior military leaders at the White House in Washington, U.S., October 7, 2019. REUTERS/Kevin Lamarque/File Photo

The official, speaking on condition of anonymity, did not disclose what military assets were under consideration.

The remarks were some of the clearest signs yet that the United States had not just halted plans for now for a full withdrawal from Syria but may add some new capabilities to strengthen those American forces that remain in the country.

“One of the most significant gains by the U.S. and our partners in the fight against ISIS was gaining control of oilfields in eastern Syria - a crucial source of revenue for ISIS,” the defense official said, using an acronym for Islamic State.

“We must deny ISIS this revenue stream to ensure there’s no resurgence.”

A second U.S. official, also speaking on condition of anonymity, said U.S. Defense Secretary Mark Esper and Army General Mark Milley, chairman of the Joint Chiefs of Staff, “continue to prepare options to take to the president.”

President Donald Trump has been softening his pullout plans for Syria after a backlash from Congress, including among key Republicans, who say he cleared the way for a long-threatened Turkish incursion against Kurdish forces in Syria who had been America’s top allies in the battle against Islamic State.

The vacuum left by Trump’s partial withdrawal also created an opening that Russia capitalized on by moving forces into the area. U.S. officials worry that Iran-backed forces in Syria could also capitalize on the chaos.

Amid fears that Islamic State could stage a comeback, Trump said on Wednesday a small number of U.S. troops would remain in the area of Syria “where they have the oil,” a reference to oilfields in the Kurdish-controlled region.

Any significant U.S. military presence on the ground would need to be properly defended from potential attack, particularly in oil-rich areas of Syria that could become targets of not just Islamic State militants but potentially, Russian-backed or Iran-backed forces operating in the country.

Republican U.S. Senator Lindsey Graham, who had been highly critical of Trump’s initial withdrawal, told reporters on Thursday: “There’s a plan coming together from the Joint Chiefs that I think may work, that may give us what we need to prevent ISIS from coming back, Iran taking the oil, ISIS from taking the oil.”

“I am somewhat encouraged that a plan is coming about that will meet our core objectives in Syria,” he said after a briefing from the Joint Chiefs chairman at the White House.

The U.S.-backed Syrian Democratic Forces (SDF), who include Kurdish militia that Ankara sees as terrorists, had cleared the region from Islamic State control and has been detaining perhaps as many as 11,000 of the militants.

“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 oilfields from falling back to into the hands of ISIS or other destabilizing actors,” the first official said.