John McCain delivers second blow to Donald Trump's Obamacare repeal plan

US Senator John McCain has said he cannot support the latest Republican bill to dismantle Obamacare, dealing it a potentially fatal blow.

The Arizona senator, who is battling brain cancer, has said he “cannot in good conscience” back the proposal.

He said he took no pleasure in announcing his opposition and noted that the bill's authors "are my dear friends."

Mr 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.

It is the second time he has voted against his party’s line on the issue.

McCain, who cast his "no" vote on the previous bill to repeal Obamacare in July just days after being diagnosed with an aggressive brain cancer, said he could not support the new 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.

Republicans have a slim Senate majority in a 100-seat chamber that they control by 52-48. The Democrats are united in opposition to the bill.

Mr McCain’s decision could doom the conservatives’ seven-year campaign to repeal former President Barack Obama’s signature legislative achievement.

With several other Republicans still undecided on the measure, Senate Majority Leader Mitch McConnell said earlier this week he intended to bring it to the Senate floor for a vote next week, though he did not promise to do so.

Mr McConnell has been trying to schedule a vote on the bill by September 30, the last day on which the bill could pass with only a simple majority of 51 votes in the Senate.

A vote taken any later than that would have to garner at least 60 votes for passage.

Weeks after the humiliating defeat in July, when the Obamacare repeal fight seemed to be over, the current bill was introduced by Republican Senators Bill Cassidy and Lindsey Graham, a close friend of McCain's, and seemed to gain momentum.