Sen. Mike Lee, R-Utah, joined four other Republican senators in opposing a procedural motion to start debate on the Senate GOP's healthcare bill.
Conn Carroll, Lee's spokesman, said the Utah Republican will not vote for the motion that allows the Senate to begin debate on the bill, called the Better Care Reconciliation Act, unless the proposal is changed.
"We have always said we won't vote to proceed on a bill we can't support," Carroll said in an email to the Washington Examiner.
Carroll said Lee is currently in negotiations to change the bill into a proposal that would earn his backing.
Republican Sens. Susan Collins of Maine, Ron Johnson of Wisconsin, Rand Paul of Kentucky and Dean Heller of Nevada have also said they plan to oppose the motion.
New: @RonJohnsonWI just told me if senate gop leadership insists on moving to h care this week he will vote against motion to proceed.
— Dana Bash (@DanaBashCNN) June 27, 2017
I want to work w/ my GOP & Dem colleagues to fix the flaws in ACA. CBO analysis shows Senate bill won't do it. I will vote no on mtp. 1/3
— Sen. Susan Collins (@SenatorCollins) June 26, 2017
Lee's opposition deals another blow to Senate Majority Leader Mitch McConnell and Republican leaders who plan to hold a vote on the healthcare bill this week.
Senate Majority Whip John Cornyn, R-Texas, said Monday Republicans "need to do it this week before double-digit premium increases are announced for next year."
He told reporters Tuesday the procedural vote on the healthcare bill would likely take place Wednesday.
With Republicans controlling 52 seats in the Senate, McConnell can only lose two votes to move forward with debate and, ultimately, final passage.
Republican leaders revealed the healthcare bill Thursday, but a handful of GOP senators have already come out against the plan in its current form.
Lee, Paul, Johnson and Sen. Ted Cruz, R-Texas, said last week they opposed the bill as it is currently written, but are open to changes.