The US Senate approved a stopgap funding bill today in a rare show of cross-party unity to avert a crippling government shutdown and keep the lights on for another two months.

The vote to fund federal agencies through 3 December passed comfortably with opposition Republicans supporting the Democrats.

It is expected to be green-lit by the House of Representatives before the midnight deadline.

"This is a good outcome, one I'm happy we are getting done," Chuck Schumer, the top Democratic senator, told colleagues on the chamber floor ahead of the vote, which was never in doubt.

"With so many things to take care of here in Washington, the last thing the American people need is for the government to grind to a halt."

The rare example of bipartisan cooperation comes with Democratic leaders trying to hammer out a deal over Mr Biden's faltering $3.5 trillion social spending package, which has no Republican support, and a bipartisan $1 trillion infrastructure bill.

Democratic progressives and moderates are deeply entrenched in a war of words over the programmes, as Republicans enjoy the disarray from the sidelines with one eye on next year's midterm elections.

The Senate-passed bipartisan infrastructure bill is due for a crucial vote in the house later today that appears to have no chance of passing, with the Democrats' left wing in open revolt.

The progressives do not trust that centrists, who object to the size and scope of the larger social spending package, will honour an agreement to pass the legislation once infrastructure is across the line.

West Virginia's Senator Joe Manchin inflamed tensions yesterday with a statement arguing that trillions of dollars in extra spending was "fiscal insanity", solidifying opposition to the smaller infrastructure bill.

He told reporters that he was unwilling to go above $1.5 trillion.

'So far so good'

Democratic House Speaker Nancy Pelosi, who said she will not put out a bill if she does not have the votes, told reporters she planned to forge ahead.

"I plan on moving forward in a positive way ... And so far so good," she told reporters.

She said Democrats were "on a path to win" the infrastructure vote, adding: "I don't want to even consider any options other than that."

Despite her optimism, the necessary support remained unlikely to materialise, leaving Ms Pelosi the option of putting the infrastructure package on ice and returning to it when the plan for the larger package is more fully formed.

This would not be a knockout blow to Mr Biden's agenda, although the delay, likely until later in autumn, would be a frustration to White House aides who risk losing momentum after spending the week marshalling lawmakers.

"It is not some major cataclysm if there isn't a vote today... This will get through. Mark my words," Energy Secretary Jennifer Granholm told CNN.

"The infrastructure bill will be passed and a version of the (social spending) bill will be as well."

A delay would also see the way clear for tempers to cool while Congress focuses on other enormous challenges, such as raising the debt limit.

The US is nerve-janglingly close to defaulting on its $28 trillion debt, with less than three weeks to go until the Treasury Department exhausts its ability to obtain new loans.

No one in the leadership of either party has spelled out a clear way to avert the crisis, which would tank the US economy and roil world markets.

Republicans are demanding that Democrats - whom they regard as profligate over-spenders - should carry the political burden of running up the debt on their own as they control Congress and the White House.

But Democrats are against using the an arcane budget process known as "reconciliation" to pass the extension without Republican support. It would take three to four weeks, they argue, making it a non-starter.

The house passed a debt limit hike yesterday on a party-line vote, but it will be dead on arrival in the Senate thanks to Republican leader Mitch McConnell's opposition.