McCain, a former Republican presidential nominee and Vietnam War hero, complained about the rushed process Republicans used to push the bill forward. He said he would consider supporting a bill like it if it had emerged from extensive hearings, debate and amendment. "But that has not been the case," he said.

McCain, who cast his "no" vote in July just days after being diagnosed with an aggressive brain cancer, said he could not support the bill without knowing how much it would cost, how it would affect insurance premiums and "how many people will be helped or hurt by it," information that will not be available until the non-partisan Congressional Budget Office provides a full assessment at the end of September.

The Graham-Cassidy bill would take federal money spent on the Medicaid program for the poor and disabled, as well as subsidies to help Americans buy private insurance, and divvy it up to the states in block grants. Advocates say that would give states more discretion to manage their own healthcare schemes.

Although the CBO has not yet fully assessed the bill's effects, independent analyzes indicate it would fundamentally redistribute federal healthcare money, generally with Republican-leaning states benefiting and Democratic-leaning states losing, largely because a majority of the states that opted to expand Medicaid under Obamacare were Democratic-leaning.

Graham said in a statement he was not giving up. "We press on," he said.

Shares of U.S. insurers gained after news that McCain would not support the bill. Insurers had fallen over the past week as investors worried about spending cuts.

Centene Corp gained 1.6 percent to $92.22 while Molina Healthcare rose 4.5 percent to $65.32. Both specialize in government-funded healthcare.

Winners And Losers Among States

State-by-state impacts from Graham-Cassidy would vary, the Axios news website reported on Friday, citing a study by the Centers for Medicare and Medicaid Services (CMS), the unit of the Department of Health and Human Services that oversees Medicaid and the Obamacare program.

The CMS study found that by 2026, Alaska would lose 38 percent of its federal funding for insurance subsidies and Medicaid; Arizona would lose 9 percent; Maine would gain 44 percent; Ohio would lose 18 percent; and West Virginia would lose 23 percent, Axios reported.