Donald Trump has urged fellow Republicans to rally behind the plan to repeal and replace Obamacare or else risk losing their seats as a result of angry voters.

The President travelled to Capitol Hill to try and cement support for the American Health Care Act, the bill crafted by Republicans to replace the Affordable Care Act, passed by Barack Obama and better known as Obamacare.

The bill is expected to be voted on by the House of Representatives on Thursday evening. But the legislation has faced intense criticism from both wings of the party.

Mr Trump and Health Secretary Tom Price urged Republicans to rally behind the bill (AP)

Conservatives believe it still provides too many “entitlements” to people, while other Republicans, along with Democrats, are concerned that an estimated 14 million people will lose their health insurance next year.

Mr Trump campaigned for the presidency with a vow to replace Obamacare, which he repeatedly said was a “disaster”. But as he and congressional Republicans have sought to find an alternative to the Democrats’ complicated, hard-won legislation, they have realised just what a challenge it is.

Mr Trump said recently: “Nobody knew healthcare could be so complicated.”

On Tuesday, Mr Trump reportedly told Republicans that they faced losing their seats if they did not back it. “We won’t have these crowds if we don’t get this done,” he said, according to Reuters.

He added: “I honestly think many of you will lose your seats in 2018 if you don't get this done.”

Trump says 'Obamacare is dead' as he prepares to repeal and replace healthcare act

House Speaker Paul Ryan, who has been the driving force behind the bill, said afterwards: “He was truly spectacular. This is part of the job that he enjoys and excels at – closing the deal.”

He said the President had told Republicans they’d made a promise to voters last year to repeal and replace Obamacare. “Now it’s time to keep that promise,” he said.

John McDonough, professor of the practice of public health at Harvard University, told The Independent that although Mr Trump’s name was not attached to the bill, he was desperate to get it passed.

“It’s his first big legislative goal and he has promoted it at the highest level,” he said. “He has a Republican-controlled House and Senate. By any normal calculation, he should be able to get the bill passed.”

Loading....

He added: “If he does not get it passed, not only would it mean failure for one of his marquee plans, it could also impact on everything else he tries to do.”

Republican leaders recrafted the bill on Monday to satisfy critics – mainly fellow Republicans – in part by proposing major changes to tax credits and provisions to alter the Medicaid insurance programme for low-income people.

The House leadership needs to win over conservatives who believe the bill does not go far enough in repealing the law.

Party leaders hope to move the legislation to the House floor for debate as early as Thursday, according to reports. But the administration and House leadership can only afford to lose about 20 votes from Republican ranks or risk the bill failing. “There are going to be adjustments made but I think we'll get the vote on Thursday,” said Mr Trump.

The Senate also will vote on the legislation and more changes could still be made.

An independent analysis of the Republican plan to replace Obamacare, has found it would leave many millions of people without heath insurance.