The Senate appears poised to advance a bill that would expand the federal government's mandate to detain immigrants who are in the country illegally, with Republicans putting the issue front and center in the new Congress.

"That's one of them. That's one of why we lost in part," the Democratic senator from Pennsylvania told Fox News.

The Senate will vote to begin debate on the Laken Riley Act, a GOP-led bill aimed at cracking down on illegal immigration that has attracted support from Democrats.