The increasing number is the latest sign of growing GOP frustration over the Trump administration's justification for the drone strike that killed Iranian Gen. Qassem Soleimani.
Sen. Tim Kaine (D-Va.) is circulating a bipartisan resolution that would direct Trump to remove U.S. forces from any hostilities against Iran within 30 days of its enactment.
GOP Sens. Mike Lee (Utah) and Rand Paul (Ky.) have already voiced their support for the measure, and Kaine says about eight more Republicans, including Sens. Susan Collins (Maine), Lisa Murkowski (Alaska), Todd Young (Ind.) and Mitt Romney (Utah), are reviewing it.
"Probably about 10," Kaine said when asked about the number of Republicans who could vote to rein in Trump's powers. "There's good discussion going on."