A senior US commander in Syria said on Monday that American troops are moving to bases, some in new locations, and working with the Kurdish-led forces to prevent a resurgence of ISIS.
Maj Gen Eric Hill said although armoured vehicles had arrived in eastern Syria, the mission’s focus had not changed.
Gen Hill said the “force mix” had an array of capabilities to deny the extremists the chance to regroup.
“The mission still continues and Daesh is trying to resurge wherever they can,” he said.
He said the forces have captured 700 ISIS fighters since its last territorial holding fell in March.
“We’ve destroyed many and war remnants and we continue to do so as we find them,” Gen Hill said.
Speaking at a remote base in Syria where the armoured vehicles arrived last week, he said the main way to do that is through working with the Kurdish-led Syrian Democratic Forces.
Coalition spokesman Col Myles Caggins said the US closed its bases in Manbij, Raqqa, Rabqa and Lafarge, with only the base at Sarrin remaining in use as part of a “deliberate withdrawal”.
Col Caggins and the SDF leader issued a call for international support over the 12,000 ISIS fighters being held in Kurdish-controlled prisons.
A spokesman for the SDF said in some cases as many as 150 prisoners were being held in a single room in improvised detention centres.
The arrival of the tanks in north-east Syria came after US troops pulled out of the region, making way for a Turkish offensive against Kurdish fighters that began last month.
Several miles away from the base, fighting between Turkish-allied fighters and the SDF was continuing, despite a ceasefire that has curbed the Turkish invasion but did not end the violence.
Smoke billowed in the distance, visible from across a major motorway that has become a frontier between Turkish-held areas and areas where US troops are going to operate.
An SDF official said Turkish shelling was continuing.
Further north, three car bombs went off on Monday in the town of Qamishli, killing at least six people, while a priest was shot dead.
ISIS claimed responsibility for the attack that killed the Armenian Catholic priest and his father as they drove from Qamishli to the city of Hassakeh, in a sign that the extremists are still active.
The US withdrawal from north-east Syria was widely criticised, even by allies of President Donald Trump.
The Kurdish-led force, deserted by Washington in the face of the threat of a military operation by a Nato ally, leaned on the Syrian government and Russia for help.
The ceasefire reached in late October left Turkey in control of a stretch of land along the border that is about 120 kilometres wide and 30 kilometres deep. But fighting south of that zone continued.
Kurdish officials say Turkey is seeking to expand its area of control.