WASHINGTON — Nearly a decade after President Barack Obama first authorized Delta Force operators to cross into Syria to help Kurdish militias beat back a genocide by the Islamic State group, the Trump administration is seizing a rare lull in hostilities across the Levant to disentangle the US military from the country.

Over the past several weeks, US troops have packed up and departed key bases in the middle Euphrates River Valley, once the heartland of the Islamic State group — and home to strategic Syrian oil and gas reserves long coveted by Russia.

Roughly a quarter of the 2,000 special ops and National Guard soldiers typically based in northeast Syria in recent years has withdrawn over the past month. Yet the Trump administration has no current plans to fully withdraw its troops from the country, US officials and a leading Republican senator indicated this week.

“It's critical that we maintain our presence there,” the chair of the Senate's Foreign Relations panel, Sen. Jim Risch (R-Ida.), told an audience at the Hudson Institute in Washington on Wednesday.