US President Donald Trump has pressed his fellow Republicans in Congress to unite behind a sweeping tax-cut bill, but apparently failed to convince a handful of holdouts who could still block a package that encompasses much of his domestic agenda.

In a closed-door meeting on Capitol Hill, Trump bluntly warned Republicans in the House of Representatives not to press for further changes to the sprawling bill, which would cut taxes and tighten eligibility for the Medicaid health program.

Trump visits Capitol Hill to rally divided Republicans around his 'big beautiful bill'. – AP

He strongly cautioned against further plans to make it more difficult for people to access Medicaid, a program for low-income Americans. "Don't mess around with Medicaid," he told them, according to a person in the room who spoke on condition of anonymity.

Trump also discouraged Republicans from seeking further carve-outs for state and local tax payments – a niche issue that is especially important for moderate Republicans in high-tax states like California and New York.

The bill would extend the 2017 tax cuts that were Trump's signature first-term legislative achievement, and also add tax breaks on income from tips and overtime pay that were part of his populist push on the campaign trail. Nonpartisan analysts say it could add $3 trillion to $5 trillion to the federal government's $36.2 trillion in debt.

But Trump failed to convince some lawmakers who are pushing for those provisions.

Republican Representative Andy Harris of Maryland, who leads the hard-right House Freedom Caucus and has been pushing for further Medicaid cuts, said:

“The president, I don't think, convinced enough people that the bill is adequate the way it is.

Republican Representative Mike Lawler, a New York moderate who is pushing to raise limits on deductions for state and local tax payments, likewise said Trump did not change his mind.

“As it stands right now, I do not support the bill," he said.

After the meeting, Trump predicted the package would ultimately pass the House, which Republicans control by a narrow majority of 220-213. 

"It was a meeting of love," he said. He did not address Harris' concerns.

As currently written, the bill would impose new work requirements on some Medicaid recipients and make other changes that would kick 8.6 million people off the program, saving $715 billion over the coming 10 years. Those changes would not take effect until 2029, and Freedom Caucus members have been pushing for them to kick in earlier. But centrists have fought to protect the program, warning that steep cuts could imperil their majority in the 2026 congressional elections.

Trump said afterward the bill would eliminate "waste, fraud and abuse" in Medicaid but would not cause people to lose coverage.

Trump is pressing for every House Republican to vote for the bill, according to a White House official. As he arrived at the Capitol, Trump said Republican lawmakers who vote against it could "possibly" face a primary challenge in next year's congressional elections.

US Speaker of the House Mike Johnson, R-La., and US President Donald Trump arrive for a House Republican conference meeting at the US Capitol in Washington. – AP

Democrats say the bill disproportionately benefits the wealthy and will take a deep bite out of social programs, but Republicans are invoking special budget rules to pass the package without their support.

House Speaker Mike Johnson aims to pass the measure by Thursday, before the Memorial Day holiday weekend, setting the stage for the Senate to take it up next month.

The Republican-controlled Congress has so far not rejected any of Trump's legislative requests.

Hanging over Republicans is a move by credit-rating firm Moody's, which last week stripped the US federal government of its top-tier credit rating. It cited multiple administrations and Congress failing to address the nation's growing debt.

If the House passes the bill, the Senate will have to labour to pass a partisan bill that could differ significantly from the House's.

Republicans control the Senate by a 53-47 margin and at least one conservative, Senator Josh Hawley of Missouri, has already stated reservations with the House's Medicaid provisions.