The bill, which would require federal authorities to detain undocumented immigrants arrested for theft-related crimes, was the first to be voted on by the newly installed Republican-controlled Senate.

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

The Senate cleared the 60-vote threshold to begin debate on a GOP priority, with Democrats backing it as the party recalibrates politically on immigration. Final passage is still uncertain.