WASHINGTON (AP) — Time running short, senators and the White House worked furiously Tuesday to salvage a bipartisan infrastructure deal, with pressure intensifying on all sides to wrap up talks on President Joe Biden’s top priority.

Despite weeks of closed-door discussions, several issues are still unresolved over the nearly $1 trillion package. Spending on public transit remains in question and a new dispute flared over the regulation of broadband access. Patience was running thin as senators accused one another of shifting the debate and picking fights over issues that had already been resolved.

Still, all sides — the White House, Republicans and Democrats — sounded upbeat that an accord was within reach as senators braced for a possible weekend session to finish the deal. No new deadlines were set.

“Good progress,” Senate Majority Leader Chuck Schumer said as he opened the chamber.

Republican negotiator Sen. Rob Portman of Ohio, who took the lead in key talks with a top White House aide, struck a similar tone, but also acknowledged the bipartisan group was “still working" on transit and other issues.

It's a make-or-break moment that is testing the White House and Congress, and the outcome will set the stage for the next debate over Biden's much more ambitious $3.5 trillion spending package, a strictly partisan pursuit of far-reaching programs and services including child care, tax breaks and health care that touch almost every corner of American life, and that Republicans vowed Tuesday to oppose.

As talks drag on, anxious Democrats, who have slim control of the House and Senate, face a timeline to act on what would be some of the most substantial pieces of legislation in years. Republicans are weighing whether they will lend their votes for Biden’s first big infrastructure lift or deny the president the political accomplishment in hopes of stopping both packages.

Biden met Tuesday morning at the White House with Sen. Kyrsten Sinema of Arizona, one of the Democratic leaders of the bipartisan talks, to discuss both the current bill and the next one.

White House press secretary Jen Psaki said after the president's meeting with Sinema that the administration sees “good signs” but is not setting any deadlines.

Ten Republicans would be needed in the evenly split 50-50 Senate to join all Democrats to advance the bipartisan bill past a filibuster toward passage, but it’s an open debate among Republicans whether it’s politically advantageous to give their support. A recent poll from The Associated Press-NORC found 8 in 10 Americans favor some increased infrastructure spending.

Republican senators sparred at their closed-door lunch Tuesday, one side arguing against doing anything that would smooth the way for Democrats' broader bill, according to a person granted anonymity to discuss the private meeting. Others spoke in favor of the bipartisan package.

The bipartisan package includes about $600 billion in new spending on public works projects.

That falls far short of what House Democrats have proposed in their own transportation bill, which includes much more spending to address rail transit, electric vehicles and other strategies to counter climate change.

At a private meeting of House Democrats on Tuesday, Rep. Peter DeFazio, D-Ore., the chairman of the House Transportation and Infrastructure Committee, called the Senate's bipartisan measure complete “crap,” according to two Democrats who attended the session.

DeFazio’s remarks illustrated the tensions between Democrats in the two chambers over the budget talks. The Democrats spoke on condition of anonymity to describe the closed-door session.

Senators in the bipartisan group have been huddling privately since they first struck an agreement with Biden in June on the contours of the joint deal. The group includes 10 core negotiators, split evenly between Democrats and Republicans, but has swelled at time to 22 members.

Filling in the details has become a grueling month-long exercise over the scope of spending in each of the categories as well as some of the underlying policies.

Transit funding has remained a stubborn dispute, as Republican senators are wary of formalizing what has been a typical formula for the Highway Trust Fund allotting around 80% for highways and 20% for transit.

Most Republican senators come from rural states where highways dominate and public transit is scarce, while Democrats view transit as a priority for cities and a key to easing congesting and fighting climate change. Democrats don't want to see the formula dip below its typical threshold.

Expanding access to broadband. which has become vital for households during the coronavirus pandemic, sparked a new debate. Republicans pushed back against imposing regulations on internet service providers in a program that helps low-income people pay for service.

Democrats were insisting on a prevailing-wage requirement, not just for existing public works programs but also for building new roads, bridges, broadband and other infrastructure, but it's not clear that will make the final package.

The senators had been debating money for public water works projects and removal of lead pipes after Sen. Mitt Romney, R-Utah, raised questions about the amount. He said Tuesday the issue had been settled.

Still unresolved is how to pay for the bipartisan package after Democrats rejected a plan to bring in funds by hiking the gas tax drivers pay at the pump and Republicans dashed a plan to boost the IRS to go after tax scofflaws.

Funding could come from repurposing COVID relief aid, reversing a Trump-era pharmaceutical rebate and other streams. It's possible the final deal could run into political trouble if it doesn't pass muster as fully paid for when the Congressional Budget Office assesses the details.

Meanwhile, Democrats are readying the broader $3.5 trillion package that is being considered under budget rules that allow passage with 51 senators in the split Senate, with Vice President Kamala Harris able to break a tie. It would be paid for by increasing the corporate tax rate and the tax rate on Americans earning more than $400,000 a year.

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Associated Press writers Alan Fram and Josh Boak in Washington and Tali Arbel in New York contributed to this report.