President Joe Biden's plan for a $1.2 trillion investment in US infrastructure will face a key step in the Senate Saturday determining if it comes to the floor for a final vote, before heading to the House of Representatives.

After spending hours trying to build consensus on Thursday, Senate Democratic Majority Leader Chuck Schumer announced just before midnight that a procedural vote would instead be set for Saturday at noon.

While he reproached Republicans for their "numerous objections" that blocked efforts to vote on amendments "all day" on Thursday, he remained confident of the bill's chances, saying earlier in the night that lawmakers were "close to an agreement."

"We very much want to finish this important bill, so we will reconvene Saturday at noon to vote on cloture."

If the bill does make it to the Senate floor on Saturday, it will need the backing of at least 10 Republicans, in addition to the 50 Democratic senators to clear the vote.

US Senate Majority Leader Chuck Schumer (2nd L) remains optimistic the bipartisan infrastructure bill will pass
US Senate Majority Leader Chuck Schumer (2nd L) remains optimistic the bipartisan infrastructure bill will pass AFP / Brendan Smialowski

It will then be submitted to a final vote by simple majority in the Senate, perhaps on the same day or on Sunday.

If approved, it will then have to be put to a vote in the House of Representatives in the coming weeks to be definitively adopted, and then signed off by the Democratic president.

That would mark a resounding victory in a deeply divided Washington for Biden, a former Senator who touts his ability to reach across the aisle.

The result of a rare consensus between Republican and Democratic senators, the ambitious plan provides for $550 billion in new federal spending on roads, bridges and transport, but also for high-speed internet and efforts to fight climate change.

It totals $1.2 trillion -- the equivalent of Spain's 2020 Gross Domestic Product -- taking into account other public funds that have already been appropriated.

That makes it "the largest long-term investment in our infrastructure and competitiveness in nearly a century," the White House said Thursday.