The US Senate has passed bipartisan legislation backed by President Joe Biden that lifts the government's $US31.4 trillion ($47.4 trillion) debt ceiling, averting what would have been a first-ever default.

The Senate voted 63-36 to approve the bill that had been passed on Wednesday by the House of Representatives, as politicians raced against the clock following months of partisan bickering between Democrats and Republicans.

The Treasury Department had warned it would be unable to pay all its bills on June 5 if Congress failed to act by then.

"We are avoiding default tonight," Senate Majority Leader Chuck Schumer said on Thursday as he steered the legislation through his 100-member chamber.

Mr Biden praised Congress' timely action.

He said he would sign it into law as soon as possible.

Mr Biden was directly involved in negotiations on the bill with House Speaker Kevin McCarthy.

While this bitter battle has ended, Senate Republican Leader Mitch McConnell wasted no time flagging the next budget fight.

Mr McConnell was referring to 12 bills Congress will work on over the US summer to fund government programs in the fiscal year beginning on October 1, which will also carry out the broad instructions of the debt limit bill.

Treasury Secretary Janet Yellen issued some pointed advice saying: "I continue to strongly believe that the full faith and credit of the United States must never be used as a bargaining chip," as Republicans did over the past several months.

Before the final vote, senators tore through nearly a dozen amendments, rejecting all of them during Thursday's late-night session in anticipation of Monday's deadline.

With this legislation, the statutory limit on federal borrowing will be suspended until January 1, 2025.

Unlike most other developed countries, the United States limits the amount of debt the government can borrow, regardless of any spending allocated by the legislature.

'Time is a luxury'

Republicans had blocked passage of any debt limit increase until they locked in some wideranging spending cuts, in a move they said would begin addressing a rapidly escalating national debt.

Mr Biden instead pushed for tax increases on the wealthy and corporations to help address the growing debt.

Republicans refused to consider any sort of tax hikes.

Both parties walled off the sprawling Social Security and Medicare retirement and healthcare programs from cuts, and Mr McCarthy refused to consider reducing spending on the military or veterans.

That left a somewhat narrow band of domestic "discretionary" programs to bear the brunt of spending cuts.

In the end, Republicans won about $US1.5 trillion in reductions over 10 years, which may or may not be fully realised.

Their opening bid was for $US4.8 trillion in savings over a decade.

Treasury technically hit its limit on borrowing in January.

Since then it has been using "extraordinary measures" to patch together the money needed to pay the government's bills.

Mr Biden, Ms Yellen and congressional leaders all acknowledged that triggering a default for lack of funds would have serious ramifications.

Those included sending shock waves through global financial markets, possibly triggering job losses and a recession in the United States, and raising families' interest rates on everything from home mortgages to credit card debt.

The Republican-controlled House passed the bill on Wednesday evening in a 314-117 vote.

Most of those who voted against the bill were Republicans.

"Any needless delay or any last-minute hold-ups would be an unnecessary and even dangerous risk."

Among the amendments debated were ones to force deeper spending cuts than those contained in the House-passed bill and stop the speedy final approval of a West Virginia energy pipeline.

Weeks of intensive negotiations

Republican senator Roger Marshall offered an amendment to impose new border controls as high numbers of immigrants arrive at the US-Mexico border.

His measure, he said, would "put an end to the culture of lawlessness at our southern border".

The Senate defeated the amendment.

Democrats said it would strip away protections for child migrants and rob American farmers of needed workers.

Some Republicans also wanted to beef up defence spending beyond the increased levels contained in the House-passed bill.

In response, Mr Schumer said the spending caps in this legislation would not constrain Congress in approving additional money for emergencies, including helping Ukraine in its battle against Russia.

"This debt ceiling deal does nothing to limit the Senate's ability to appropriate emergency supplemental funds to ensure our military capabilities are sufficient to deter China, Russia and our other adversaries, and respond to ongoing and growing national security threats, including Russia's evil ongoing war of aggression against Ukraine," Mr Schumer said.

The bill was cobbled together over weeks of intensive negotiations between senior aides for Mr Biden and Mr McCarthy.

The main argument was over spending for the next couple of years on discretionary programs such as housing, environmental protections, education and medical research that Republicans wanted to cut deeply.

The nonpartisan Congressional Budget Office estimated the bill would save $US1.5 trillion over 10 years.

That is below the $US3 trillion in deficit reduction, mainly through new taxes, that Mr Biden proposed.

The last time the United States came this close to default was in 2011.

That stand-off hammered financial markets, led to the first-ever downgrade of the government's credit rating and pushed up the nation's borrowing costs.

There was less drama this time as it became clear last week that Mr Biden and Mr McCarthy would find a deal with enough bipartisan support to get through Congress.

Reuters