A jubilant Trump said the bill's passage would supercharge the US economy "into a rocket ship", glossing over deep concerns within his own Republican Party that it will balloon the national debt and gut health and welfare support.

Speaking to reporters as he headed for a rally in Iowa to kick off America's 250th birthday celebrations, the president called the spending package "the biggest bill of its kind ever signed."

A small group of Republican opponents finally fell into line after Speaker Mike Johnson worked through the night to corral dissenters in the House of Representatives behind the "One Big Beautiful Bill."

The bill squeezed past a final vote, 218-214. The White House declared "VICTORY" on social media and said Trump would sign the bill into law on Friday, the July 4th Independence Day holiday.

The timing of the vote had slipped back to Thursday as Democratic House minority leader Hakeem Jeffries spoke against the bill for nearly nine hours to delay proceedings.

Mass deportations, tax breaks

The legislation is the latest in a series of big wins for Trump, including a Supreme Court ruling last week that curbed lone federal judges from blocking his policies, and US air strikes that led to a ceasefire between Israel and Iran.

His sprawling mega-bill narrowly passed the Senate on Tuesday and had to return to the lower chamber for a rubber stamp of the senators' revisions.

The package honors many of Trump's campaign promises: boosting military spending, funding a mass migrant deportation drive and committing US$4.5 trillion to extend his first-term tax relief.

"Everything was an absolute disaster under the Biden-Harris radical regime, and we took the best effort that we could, in one big, beautiful bill, to fix as much of it as we could," Johnson said.

"And I am so grateful that we got that done."

But it is expected to pile an extra $3.4 trillion over a decade onto the country's fast-growing deficits, while shrinking the federal food assistance program and forcing through the largest cuts to the Medicaid health insurance scheme for low-income Americans since its 1960s launch.

Some estimates put the total number of recipients set to lose their insurance coverage under the bill at 17 million. Scores of rural hospitals are expected to close.

While Republican moderates in the House fear the cuts will damage their prospects of reelection next year, fiscal hawks chafed over savings that they say fall far short of what was promised.

Johnson had to negotiate tight margins, and could only lose a handful of lawmakers in the final vote, among more than two dozen who had earlier declared themselves open to rejecting Trump's 869-page text.

Trump spent weeks hitting the phones and hosting White House meetings to cajole lawmakers torn between angering welfare recipients at home and incurring the president's wrath.

Democrats hope public opposition to the bill will help them flip the House in the 2026 midterm election, pointing to data showing that it represents a huge redistribution of wealth from the poorest Americans to the richest.

Jeffries held the floor for his Democrats ahead of the final vote, as he told stories of everyday Americans who he argued would be harmed by Trump's legislation.

"This bill, this one big, ugly bill, this reckless Republican budget, this disgusting abomination, is not about improving the quality of life of the American people," he said. 

After the bill was passed, Trump predecessor's Joe Biden said it was "not only reckless, it's cruel."

Extra spending on the military and border security will be paid in part through ending clean energy and electric vehicle subsidies, a factor triggering a bitter public feud between Trump and former key advisor Elon Musk.