The vote on President Donald Trump's healthcare bill is on a knife-edge, with Republicans still split despite projections of confidence from House of Representatives leadership that the legislation will pass.

The House is expected to vote on the bill to repeal and replace Obamacare on Thursday afternoon, after two failed attempts to do so earlier this year. With firm and united Democratic opposition to GOP efforts, Republican leaders and Mr Trump have had to push hard to find common ground on a bill in a diverse and sometimes divided party.

“It's time to live or die by this day,” Republican leaders told the rank and file at an early morning, closed-door meeting to rally support, said Florida Representative Dennis Ross. House majority leader Kevin McCarthy said the legislation “will pass.”

The latest version of the healthcare bill would make it possible for states to avoid requirements in the Affordable Care Act to provide a menu of basic health services like preventative care. It would also eliminate fines imposed on people who don’t buy insurance and cut Medicaid funding for the poor. An eleventh-hour deal made between two Republicans and Mr Trump himself would provide $8 billion over five years to help people with pre-existing illnesses, such as asthma or heart disease, afford coverage.

A previous version of the bill — which is opposed by the American Medical Association, the AARP, and other medical groups — would have bumped an estimated 24 million people off of insurance by 2026, according to an analysis by the Congressional Budget Office. Those figures scared moderate Republicans concerned about the political pitfalls of forcing their constituents off of insurance. The new bill will be voted on without an updated analysis of its impact.

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Republican representative Mark Sanford told CNN that his party moved too quickly to pass the healthcare bill.

House minority leader Nancy Pelosi emphasised in a press conference that 'Trumpcare' destroys protections for people with pre-existing conditions. She cited a study from Karen Pollitz, a healthcare expert at the Kaiser Family Foundation, who found that the additional $8 billion would only cover costs for about 1 percent of those who purchase insurance on the exchanges created by Obamacare.

Ms Pelosi has previously said that Republicans have made the new healthcare legislation “even more dangerous and destructive than the last time they brought it to the floor,”

Mr Trump has struggled to secure significant legislative victories since taking office in January. The president played an important role in pushing for the latest version of the healthcare repeal bill, at times personally contacting lawmakers to ask for their support.

On the other side of Congress, Republican senator Bob Corker said that the Senate hasn’t been focused on a healthcare bill just yet and that plans haven’t been laid out for what to do when the House sends a bill over. One thing is for certain, though: The House bill won’t have an up or down vote when it is sent over.

“No. Zero chance,” Mr Corker said on MSNBC when asked about the House bill getting a vote without Senate tinkering.