A months-long negotiation on infrastructure between the White House and US lawmakers is coming to a head, with President Joe Biden desperate to woo Republicans while also keeping centrists and climate-concerned progressives in his party on board.

Ten moderate senators -- five Democrats and five Republicans -- announced a tentative agreement Thursday aimed at improving and expanding the nation's crumbling roads, bridges, ports, pipes, tracks and broadband internet.

In a joint statement they said they were "optimistic" that the plan -- which they stressed would not raise tax rates -- could garner broad support from both parties and make it to the president's desk.

There is growing urgency to reach a final deal in the coming weeks, as a crowded congressional calendar is on the horizon.

US President Joe Biden said his infrastructure plan would be a once-in-a-generation investment in America, but lawmakers from both parties are scrambling to reach even a basic deal to rebuild the country's crumbling roads, bridges, ports and pipes
US President Joe Biden said his infrastructure plan would be a once-in-a-generation investment in America, but lawmakers from both parties are scrambling to reach even a basic deal to rebuild the country's crumbling roads, bridges, ports and pipes POOL / Leon Neal

But with all sides acutely aware of the time crunch, liberal Democrats voiced their displeasure Friday at what has been left out of the bipartisan framework -- and signalled it might already be dead in the water.

"NO way that I'm supporting an infrastructure package that doesn't invest in fighting the climate crisis," tweeted congresswoman Pramila Jayapal, who chairs the Congressional Progressive Caucus. "Who's with me?"

"We cannot allow climate denial to masquerade as bipartisanship," added Senator Ed Markey after the moderates announced an agreement. "No climate, no deal."

Biden's initial $2.3 trillion American Jobs Plan was a mammoth proposal aimed at rebuilding the nation's crumbling infrastructure.

But it also sought to raise wages for home care workers, improve child care facilities, expand affordable housing and access to social welfare Medicaid services and, most notably, reduce the impacts of climate change.

Protesters with the Sunrise Movement rallied in front of the White House against what they say is slow action on infrastructure legislation, job creation and addressing climate change
Protesters with the Sunrise Movement rallied in front of the White House against what they say is slow action on infrastructure legislation, job creation and addressing climate change AFP / SAUL LOEB

Republicans balked at the plan's price tag, and stressed that elements unrelated to traditional infrastructure be kept out.

Earlier talks between Biden and Republican senators collapsed this week.

And while the latest bipartisan plan -- reported at $1.2 trillion over eight years, with $579 billion of it being new spending -- raised hopes, it quickly became clear how big the hurdles are.

Fixing America's roads, bridges and ports is a popular talking point for US lawmakers, but genuine large scale acton on infrastructure in the country is rare
Fixing America's roads, bridges and ports is a popular talking point for US lawmakers, but genuine large scale acton on infrastructure in the country is rare AFP / JIM WATSON

"Dems are burning precious time & impact negotiating w/GOP," House Democrat Alexandria Ocasio-Cortez tweeted on Wednesday.

But top Republican Mitch McConnell's plan "is to run out the clock," she added. "It's a hustle. We need to move now."

The popular lawmaker's message to the White House was clear: stop waiting for a unicorn deal to emerge with Republicans, and craft a bill that incorporates Democrats' priorities including addressing climate change.

There is quicksand in both chambers of Congress, however.

"We're trying to get an outcome on infrastructure. Something that is popular on both sides of the aisle," McConnell told Fox News on Thursday.

"All we're insisting on is that the infrastructure bill be about infrastructure and not a whole lot of other things and that it be credibly paid for," he added.

And with the Senate evenly split 50-50, Biden would need 10 Republicans to join all Democrats in order to override the opposition party's filibuster -- unless he uses a process known as reconciliation.

Such a path allows budget-related legislation to pass the Senate with a simple 51-vote majority, rather than the 60 needed to thwart the filibuster.

"Why let Republicans decide the size of an infrastructure bill when reconciliation is a perfectly legitimate process (used unapologetically by the GOP when they were in power)," Senator Chris Murphy asked.

"It's not cheating to use the rules."

But with the no room for defections, Biden would need all 50 Democrats on board for any reconciliation measure, and there is already one Senate Democrat, Joe Manchin, who says he is holding out for a bipartisan deal.

Other Democrats are suggesting passing the slimmed down bipartisan infrastructure package, but only with a reconciliation bill on the other priorities moving at the same time.

Biden, who said last month that a good infrastructure plan would create the "foundations of a strong, fair and resilient competitive economy," is in Europe this week.

But he pledged to remain in contact with lawmakers in Washington as they negotiate.