A bipartisan group of senators tentatively reached an agreement with White House officials Wednesday on hundreds of billions of dollars in new spending for the nation’s infrastructure system, giving a significant boost to one of President Biden’s biggest domestic policy ambitions.

Multiple senators leaving an evening negotiating session at the Capitol said the group — which included five Democrats, five Republicans and top White House officials — had reached a framework of a deal. They said senators would go to the White House on Thursday to brief Biden on the details.

“There’s a framework of agreement on a bipartisan infrastructure package,” Sen. Susan Collins (R-Maine) said as she left the meeting. “There’s still details to be worked out.”

On June 20, amid bipartisan infrastructure talks, the Biden administration and Congress were still discussing how to pay for an infrastructure plan. (The Washington Post)

Senators declined to disclose details of their agreement but stressed that the group had agreed not just on the spending levels for various infrastructure projects but also on how to pay for the package. An earlier framework reached by the senators — which did not have White House approval — included $974 billion in spending over five years, $579 billion of which was for new projects and initiatives.

One official directly familiar with the framework said the revised level was $559 billion in new spending because senators planned to repurpose about $20 billion that had been allocated to broadband projects, although others close to the negotiations disputed how that figure was tabulated.

“White House senior staff had two productive meetings today with the bipartisan group of Senators who have been negotiating about infrastructure,” White House press secretary Jen Psaki said in a statement Wednesday. “The group made progress toward an outline of a potential agreement, and the President has invited the group to come to the White House tomorrow to discuss this in-person.”

Other tasks that remain for the bipartisan group of Senate negotiators include briefing their leadership and their respective caucuses. But, Collins said, “I’m optimistic that we’ve had a breakthrough.”

White House officials huddled with Democratic leaders immediately after the negotiations concluded Wednesday night on Capitol Hill, a sign they were already planning next steps. Senate Majority Leader Charles E. Schumer (D-N.Y.) said “we support the concepts that we heard about,” but he deferred further comment until the agreement was officially announced.

It is less clear whether GOP leaders will sign off on the package. White House officials have said it would be politically treacherous for Republican leaders to oppose a bipartisan infrastructure package that would improve highways, roads and bridges across the United States and create many jobs.

The 10 senators — Collins, Bill Cassidy (R-La.), Joe Manchin III (D-W.Va.), Lisa Murkowski (R-Alaska), Rob Portman (R-Ohio), Mitt Romney (R-Utah), Jeanne Shaheen (D-N.H.), Kyrsten Sinema (D-Ariz.), Jon Tester (D-Mont.), and Mark R. Warner (D-Va.) — have met numerous times with the administration’s negotiators this week. Steve Ricchetti, counselor to the president; Louisa Terrell, legislative affairs director, and National Economic Council Director Brian Deese have been representing the administration in the talks.

Asked about the negotiations at the White House earlier Wednesday, Biden said: “I’ll tell you that when I get the final numbers tonight.”

Although the agreement could amount to one of the most significant investments in infrastructure in recent years, the tentative bipartisan deal still falls far short of Biden’s initial $2.2 trillion vision that he outlined in what he called the American Jobs Plan earlier this year. In that plan, he proposed paying for new spending by raising the corporate tax rate from 21 percent to 28 percent. The White House has released a separate $1.8 trillion package meant to invest in “human infrastructure” such as education and paid leave.

Many Republicans objected to the idea of raising the corporate tax rate, however, and White House officials have looked for alternatives that would help them offset the new costs.

Democratic leaders have long said Biden’s expansive infrastructure agenda could pass through multiple tracks, meaning one bipartisan package that spends money on traditional public-works projects and another that funds Democratic priorities could pass using a special budgetary process that circumvents a filibuster in the Senate.

Schumer and House Speaker Nancy Pelosi (D-Calif.) met with administration officials Wednesday night on Capitol Hill to begin mapping out both legislative strategies for the president’s plan.

Behind the scenes, Senate negotiators and administration officials tussled primarily over how to pay for the package. Unraveling the 2017 GOP tax law, which significantly lowered the tax rate for corporations, was a nonstarter for Republicans. The bipartisan group initially proposed indexing the gas tax to inflation to raise additional revenue, but the White House said doing so was off limits.

Details were not clear Wednesday night about how exactly the group would pay for its package. More information was expected Thursday after the senators finished briefing Biden at the White House.

Manchin said the broad contours of the spending levels in the package had not changed.

“We owe it to the president to bring him up to speed on everything and they run the numbers, too, to make sure all the numbers we have are accurate,” he said.

Marianna Sotomayor contributed to this report.