The Republican-led US Congress narrowly passed Donald Trump's flagship spending bill Thursday after a marathon voting session on the package, which is set to slash social welfare programs and add more than $3 trillion to the national debt.

The text, headlined by a $4.5 trillion renewal of the president's first-term tax cuts, was approved by the House of Representatives along party lines, delivering Trump the biggest legislative win of his second term.

The US President will sign his "big beautiful" tax and spending bill in a ceremony on Independence Day on Friday after it passed Congress, the White House said.

The bill "will be at the president's desk for signature at a big, beautiful signing tomorrow at 5 pm on the Fourth of July, just as the president always said and hoped it would be," Press Secretary Karoline Leavitt said in a call with reporters Thursday.

Trump hailed the passage of his flagship tax and spending bill Thursday by Congress, saying it would boost the US economy like a "rocket ship."

"It's going to make this country into a rocket ship," Trump told reporters as he headed for a rally in Iowa to kick off America's 250th birthday celebrations, calling it the "the biggest bill of its kind ever signed."