President Biden vowed Monday that the size and scope of his $2.25 trillion jobs plan — as well as how to pay for it — is up for negotiation, setting the stage for what is likely to be months of congressional wrangling on one of the White House’s chief legislative priorities.

Whether a bipartisan deal ultimately materializes is far from clear, however, as a top GOP senator told Biden in a private Oval Office meeting Monday that it would be “almost impossible” to win over Republicans if the plan envisions boosting the corporate tax rate, as it currently does. There is also widespread private skepticism among congressional Republicans that the White House is genuinely open to a cross-party agreement that might significantly scale back Biden’s ambitions.

But the president, as well as White House officials, insisted that his overtures at bipartisanship were earnest and that he would not have been spending hours meeting with Republicans otherwise.

“I’m not big on window-dressing, as you’ve observed,” Biden said as he prepared to convene the meeting with lawmakers of both parties.

The session, which a White House official said was the first of several Biden will host this month, marked the informal beginning of months of arm-twisting and vote haggling on Capitol Hill to line up support behind the administration’s American Jobs Plan, a proposal that stretches beyond the traditional definitions of infrastructure.

The ambitious plan forms the cornerstone of Biden’s economic agenda and includes Democratic priorities that the White House and hope to enact before the 2022 midterms. Despite the president’s stated appetite for bipartisanship, the infrastructure bill has received little interest from Republicans so far, particularly with Biden’s proposal to finance it by raising taxes on corporations from the current 21 percent to 28 percent.

On March 31, President Biden outlined a massive $2 trillion infrastructure proposal. Here’s what’s included in the plan and how it’s funded. (Blair Guild/The Washington Post)

Under former president Donald Trump, Republicans passed a bill cutting the corporate taxes from the then-rate of 35 percent to 21 percent, and few are willing to consider reversing that, even in part.

“I view the 2017 tax bill as one of my signature achievements in my entire career,” Sen. Roger Wicker (R-Miss.) said. “It would be an almost impossible sell for the president to come to a bipartisan agreement that included the undoing of that signature.”

Biden gathered with lawmakers including Sen. Maria Cantwell (D-Wash.), who chairs the Senate Commerce Committee, and Wicker, her GOP counterpart. The panel plays a critical role in congressional debates on railroads and broadband Internet access, major elements of the Biden infrastructure plan.

President Biden has pushed for bipartisanship even as congressional Democrats have signaled that they may push through his agenda items without GOP votes. (JM Rieger/The Washington Post)

Reps. Garret Graves (R-La.) and Donald M. Payne Jr. (D-N.J.), meanwhile, who also took part in the meeting, belong to a panel of House lawmakers considering legislation to fund and improve the nation’s highways while implementing new programs to reduce carbon emissions.

Other attendees at the meeting included Sen. Alex Padilla (D-Calif.), Sen. Deb Fischer (R-Neb.), Rep. David E. Price (D-N.C.) and Rep. Don Young (R-Alaska). Young is the currently the longest-serving member of the House, and Biden affectionately called him the “dean.”

“The president made a compelling case for acting big and broadly when it comes to the definition of infrastructure,” Padilla said. The freshman senator, who assumed Kamala D. Harris’s Senate seat when she was elevated to the vice presidency, said Biden’s message was that simply catching up on deferred maintenance on roads and bridges would be a significant lost opportunity.

Biden was attuned to the particulars of his plan, attendees said, with Padilla saying the president was particularly animated in his support for the billions of dollars outlined in his proposal that would pay for upgrades to medical centers run by Veterans Affairs.

Padilla also made a case that the administration could consider not paying for parts of the infrastructure and jobs plan — echoing the view of some other Democrats — although other attendees and people briefed on the meeting said Biden didn’t appear too keen on deficit financing. The president also said he opposed raising gasoline taxes to finance parts of the plan, the White House later confirmed, despite suggestions from some Republicans that he consider doing so.

Speaking with reporters after the session, Payne said Republicans raised many issues “with parts of the bill,” including the size of the package, its policy scope and the White House’s preferred means of paying for it.

“The president was much more flexible than I was,” Payne added. “I believe that the American Jobs Plan is a once-in-a-lifetime generational opportunity for us to modernize our airports, our roadways, our rail stations and our water infrastructure, and it’s long overdue.”

Wicker confirmed he and other Republicans wanted to stick with what they have described as traditional infrastructure — such as ports, rails and roads — and also noted there is $40 billion in unspent federal dollars to upgrade the nation’s broadband system.

Young agreed that lawmakers have to be cognizant about the “very definition of infrastructure,” adding that he told Biden the White House should reconsider implementing an increase in the gasoline tax.

“Roads, bridges, and ports are undoubtedly infrastructure, and I believe that energy grids, broadband, and clean water can fit the definition as well,” Young said. “But I have concern that moving too far beyond this could sink the bill.”

The president has insisted his outreach to Republicans is genuine, given the broad political appeal of addressing the country’s infrastructure needs. But the administration has also signaled that if negotiations drag on, Democrats may decide to act on their own, as they did in approving a $1.9 trillion coronavirus relief package in March.

“I’m confident everything is going to work out for us perfectly,” Biden said Monday.

Still, the pathway to passage has become more complicated since the White House formally unveiled its plan March 31. Republican lawmakers have argued that certain elements, including those that tackle climate change and $400 billion in elder care, do not belong in an infrastructure package.

Senior Republicans, including Senate Minority Leader Mitch McConnell (R-Ky.), also took issue with the price tag and the tax increases Biden has put forward to pay for it. Some Democrats, including centrist Sen. Joe Manchin III of West Virginia, have raised their own objections to the tax hikes.

Manchin also warned the Biden administration and Democratic leaders last week that the party should not repeatedly rely on an arcane legislative maneuver known as reconciliation to advance an infrastructure package with only 51 votes.

But other Democratic senators are pushing for prompt, ambitious action, saying Republicans in the Obama years clearly showed they have no real interest in bipartisanship or compromise.

“This country faces enormous crises,” said Sen. Bernie Sanders (I-Vt.), the chairman of the Senate Budget Committee who is crafting the party’s reconciliation strategy. “I think the American people are not staying up nights worrying about the process. They want results.”

Before Monday’s meeting, the White House sought to pressure lawmakers by providing fact sheets showing how years of underfunded initiatives in all 50 states have resulted in poor roads, bridges, waterways and broadband connections. In Manchin’s home state of West Virginia, the White House pointed to more than 1,500 bridges and 3,200 miles of highway in “poor condition,” adding, “The need for action is clear.”

Jeff Stein contributed to this report.