"The oil is so valuable for many reasons," Trump said from the White House Diplomatic Room after announcing the death of ISIS leader Abu Bakr al-Baghdadi. "It fueled ISIS, number one. Number two, it helps the Kurds, because it's basically been taken away from the Kurds. And number three, it can help us. We should be able to keep some also."
He repeated that he may try to persuade an American energy company to extract the oil and bring it to market, though so far no company has publicly expressed interest in taking on the risks associated with working in the country.
The U.S. "may have to fight for the oil," he said. "It's OK."
He said anyone trying to take the oil will have a "helluva fight" on their hands.
The oil fields are in territory now controlled by the Kurdish-led Syrian Democratic Forces, Republican South Carolina Sen. Lindsey Graham said from the White House briefing room after Trump's remarks.
He called securing the oil "good, commonsense foreign policy."
"The way he secured this, it's a win-win," Graham said.
Russia's Defense Ministry on Saturday harshly criticized the U.S. decision to send armored vehicles and combat troops into eastern Syria to protect oil fields, calling it "banditry."
A U.S. convoy of over a dozen vehicles was spotted driving south of the northeastern city of Qamishli, likely heading to the oil-rich Deir el-Zour area where there are oil fields, or possibly to another base nearby.
The Associated Press contributed to this report.