KABUL - The United States is considering keeping some troops in northeastern Syria to stop oil falling into the hands of Islamic State or others but no decision has yet been made, Defense Secretary Mark Esper said.

President Donald Trump decided earlier this month to withdraw all 1,000 US troops from the region, a move widely criticized as a betrayal of Kurdish allies who had fought for years alongside them against Islamic State.

US troops crossed into Iraq early on Monday as part of the withdrawal process. Trump began pulling US troops back from northeastern Syria in early October.

"We have troops in towns in northeast Syria that are located next to the oil fields, the troops in those towns are not in the present phase of withdrawal," Esper told reporters during a visit to Afghanistan.

"The purpose is to deny access, specifically revenue to ISIS (Islamic State) and any other groups that may want to seek that revenue to enable their own malign activities," he said.

Esper said there had been discussions about keeping some of the US troops, who were with the Syrian Democratic Forces (SDF), in place. He said he had not presented that option yet, but the Pentagon's job was to look at different options.

Reuters