Sen. Susan Collins, R-Maine, will not support the current House GOP healthcare bill, the Portland Press Herald reported.
The legislation being debated in Congress "really misses the mark" – she said in her most definitive opposition to a bill she has already raised concerns about, according to the report.
"This is not a bill I could support in its current form," she told the newspaper.
Collins pointed to the Congressional Budget Office's analysis of the bill earlier this week, which found 24 million more people would be uninsured by 2026 under the plan.
In particular, she noted her concern about the CBO finding low-income people and seniors would have to pay far more for insurance under the House GOP bill than under Obamacare.
"This bill doesn't come close to achieving the goal of allowing low-income seniors to purchase health insurance," she said. "We don't want to in any way sacrifice coverage for people who need it the most."
One possible change to the bill being pushed by some Republicans is to increase the tax credits for the poor and seniors to alleviate the affordability problems, The Hill reported.
"This is so complex," Collins said. "It's important we do this right."
The Press Herald reported, as one of a handful of moderates in the House, Collins is considered a key vote that could determine whether an Obamacare repeal and replacement bill could be approved.