US troops need to remain in Syria to counter the Islamic State (ISIS) and prevent its resurgence, Defense Secretary Lloyd Austin said on Wednesday, citing the risks posed by tens of thousands of ISIS fighters held in Kurdish-controlled prisons.

“I think ISIS fighters would enter back into the mainstream” if US forces leave Syria,” Austin told the Associated Press. “We still have work to do in terms of keeping a foot on the throat of ISIS.”

Increased US Troop Presence

The US has recently increased its troop presence in Syria from 900 to approximately 2,000 following the ousting of Bashar al-Assad’s regime by a coalition of rebels led by Hay’at Tahrir al-Sham (HTS) on December 8. The surge, described as a temporary measure, is aimed at preventing ISIS from regaining a foothold in the region.

Kurdish-Led Forces at Risk

US forces are the primary backers of the Kurdish-led Syrian Democratic Forces (SDF), which played a key role in defeating ISIS territorially in 2019. The SDF continues to manage detention camps housing more than 10,000 ISIS fighters.

“At some point, the SDF may very well be absorbed into the Syrian military, and then Syria would own all the [ISIS detention] camps and hopefully keep control of them,” Austin said, acknowledging the SDF as “good partners.”

However, attacks by Turkey and Turkish-backed Syrian National Army (SNA) militia groups are pressuring Kurdish-held territories in the north. This has forced the SDF to redeploy resources away from anti-ISIS operations to secure the northern frontlines.

Concerns Over Detainees

US Secretary of State Antony Blinken also highlighted the risks posed by ISIS detainees. “An even more acute danger would be if the more than 10,000 foreign terrorist fighters who are being detained under the vigilance of our Kurdish friends in Syria were to get out and reconstitute,” Blinken said, emphasizing the ongoing threat posed by ISIS.

Regional Tensions

Turkey views the People’s Protection Units (YPG), the backbone of the SDF, as the Syrian branch of the Kurdistan Workers’ Party (PKK), a designated terrorist organization in Turkey. This has further complicated the security situation in northern Syria.

The US remains committed to maintaining its military presence to ensure that ISIS cannot exploit these tensions and regain strength in the region.