WASHINGTON — A small bipartisan group of senators is privately sketching out the contours of a new infrastructure package — and fresh ways to pay for it — that they hope to sell to colleagues after negotiations between Republican senators and the White House stalled in recent days.

The nascent plan is being drafted by a more than a half-dozen lawmakers including Republican Sens. Mitt Romney of Utah and Rob Portman of Ohio as well as Sen. Joe Manchin, D-W. Va. On Tuesday, Romney said the group has come to a "pretty close consensus" on key elements of a blueprint that focuses largely on traditional infrastructure, such as roads, bridges, trains and broadband internet.

"We're not very far from the Biden proposal on areas where we both think it's appropriate for an infrastructure bill," Romney told The Washington Post on Tuesday.

The still-forming compromise is expected to jettison some of President Joe Biden's proposals that have struggled to attract Republican support, including his plan to couple infrastructure investments with new federal aid targeting elder care and low-income families. Gone, too, are likely to be president's proposed funds for electric vehicles, Romney said.

For these lawmakers, any attempt to unwind the 2017 GOP tax cuts is still off the table. In its place, the senators are proposing a menu of alternate ways to pay for it, including unused stimulus funds to finance infrastructure improvements. Romney said they also would seek to rethink the way vehicle owners pay taxes — tying the gas tax to inflation, for example, while requiring owners of electric vehicles for the first time to pay similar fees. And the group has proposed generating revenue by better enforcement of current tax laws, Romney said.

It is unclear if the emerging plan can win over spending-wary Republicans and Democrats who want to seize on their slim but potent majorities in Congress to usher in significant changes to the U.S. economy. Biden, meanwhile, has vehemently opposed paying for infrastructure in a way that would raise taxes on Americans making under $400,000 annually, a pledge that the lawmakers' still-forming proposal is likely to violate.

But narrowing the definition of infrastructure at least has earned the critical support of lawmakers including Manchin, who said Tuesday he thought the White House had already agreed to tackle it in a "separate package."

The dispute in the meantime has soured formal talks between GOP leaders and the White House over a bipartisan deal. Republicans on Tuesday again alleged that Biden previously had agreed to take what they see as "social" spending off the table — only for his aides to reverse course days later.

Both sides still insist they are not finished negotiating, however, and Sen. Shelley Moore Capito, R-W.Va., said her party plans to present its next counter-offer to the Biden administration on Thursday. The offer is expected to be around $1 trillion, according to Sen. Roger Wicker, R-Miss.

"We're going to hit a figure, very close to what the president said he would accept," he said.

The scramble to strike a deal comes at a moment of great uncertainty in the infrastructure debate. The White House has issued a Memorial Day deadline by which it hopes to see progress, but it hasn't exactly explained what that means, leaving lawmakers on both sides unsure if the president is ready to try to advance another one of his economic priorities entirely through Democratic votes.

Ratcheting up the pressure, Senate Majority Leader Chuck Schumer, D-N.Y., on Tuesday said he plans to move forward on infrastructure reform in July.In the meantime, Democrats including Manchin have signaled they are not yet ready to abandon bipartisanship — and pursue infrastructure using the same legislative maneuver that helped the party adopt a $1.9 trillion coronavirus aid package earlier this year. Without the support of Manchin and the rest of the party's lawmakers, the White House's threats to sidestep Republicans risk carrying little weight.

"If the place works," Manchin said, "let it work."

It was only two weeks ago that Biden and his GOP counterparts met in the Oval Office for the first formal round of talks — a session both sides described as positive and productive as they affirmed their interest in securing a bipartisan deal. But Democrats and Republicans since then have struggled to find common ground, warring over even the definition of what qualifies as infrastructure in the first place.

Capito last week put forward a counter-offer on behalf of her party that largely left the scope of her package unchanged. She raised the price tag — from $568 billion to roughly $800 billion — only by extending the life of the proposal from five to eight years. Much of the money in her early blueprint still reflected planned or existing federal spending, frustrating Democrats who saw it as insufficient.

The White House followed days later by similarly standing its ground, keeping intact the president's proposed social spending and his plan to pay for infrastructure reforms through tax increases on corporations. The move drew sharp rebukes from GOP lawmakers, who said the tax hikes in particular are still political nonstarters that would prevent them from supporting any deal.

With seemingly no solution in sight, Republicans left the last round of negotiations Friday on a dour note, expressing a fear that the two sides had only grown further apart. The finger-pointing only intensified Monday, as Capito and her colleagues blamed the impasse on White House aides. Republicans alleged that Biden had been open to some of the changes they sought — specifically to take entire categories of spending off the table — only to have his staff reverse course.

The White House did not explicitly dispute those accusations, but press secretary Jen Psaki and other officials still faulted the GOP publicly for a counter-offer that they say didn't move far enough — and encouraged Republicans to send another in the coming days.