A bipartisan group of senators sketching out an infrastructure proposal expanded their base of support Wednesday, even as they continue to haggle over how to pay for billions of dollars in new spending in line with President Biden’s vision for a massive overhaul of the nation’s public works system.

The show of support, the senators said, marked an attempt to prove publicly that their new endeavor can win broad approval on Capitol Hill, even as an increasingly agitated liberal coalition has raised alarms that the drawn-out bipartisan talks have been fruitless — and some conservatives have questioned the need for another massive burst in federal spending.

“We support this bipartisan framework that provides an historic investment in our nation’s core infrastructure needs without raising taxes,” the group of Democrats and Republicans said in the statement.

Even as they rallied support for their plan, however, Senate Democrats huddled privately Wednesday to devise a path forward for trillions of dollars in additional spending in infrastructure improvements and other economic initiatives that may not make it into a bipartisan deal.

Senate Democrats, Republicans prepare to sell nearly $1 trillion infrastructure plan to White House.

In the meantime, Democratic senators who helped craft the bipartisan plan met Wednesday with Biden’s top aides — including Steve Ricchetti, counselor to the president; Brian Deese, director of the National Economic Council; and Louisa Terrell, the White House’s legislative affairs director — to update the administration on their efforts, according to a White House official.

“The White House team was grateful for the briefing from the Democratic senators involved in the infrastructure negotiations, and found it productive and encouraging," White House spokesman Andrew Bates said in a statement.

The bipartisan Senate plan calls for about $974 billion in infrastructure spending over five years, according to people who spoke on the condition of anonymity because they weren’t authorized to reveal the details.

Biden had originally requested more than $2 trillion in new infrastructure spending, but White House officials had signaled they were willing to consider a package closer to $1 trillion.

After the meeting, Portman said senators plan to brief the fuller House caucus this week, reflecting their strategy of “going out in concentric circles now and bringing in more and more people.”.

The developments came as Senate Democrats on Wednesday laid the early groundwork to chart their own course on trillions of dollars in additional spending on infrastructure and the party’s vast additional economic priorities

Many party lawmakers have made clear they would not support any bipartisan infrastructure deal emerging in the Senate unless they could move their robust reconciliation package essentially in tandem