President Joe Biden kicked off a day of meetings Tuesday with two key moderate lawmakers – Sens. Kyrsten Sinema, D-Ariz., and Joe Manchin, D-W.Va. – to try and close the deal on one of the two major legislative pieces of his domestic agenda as Congressional Democrats work to narrow the scope of his $3.5 trillion budget measure.

Biden met separately with Manchin and Sinema as they work to come up with a final number, a source familiar with the meeting told The Associated Press. White House press secretary Jen Psaki later confirmed the separate meetings, and said the president felt his time with Sinema was "constructive" and that he "felt the ball move forward." 

Sen. Manchin and President Biden had not yet completed their own closed-door meeting at the time of Psaki's remarks.

"Senator Sinema had a meeting with the president earlier today," Psaki confirmed at a press briefing in the early afternoon. "They had a constructive meeting and agreed that we're at a pivotal moment and need to continue to work to finalize the path forward. He asked his team to follow up later this afternoon with her directly to continue the conversation and continue the discussions." 

Psaki pointed reporters to Sens. Manchin and Sinema when asked where the group landed on top-line numbers, but said it is "obviously in a very sensitive time right now in these discussions, a pivotal time in these discussions."

With Republicans expected to vote against the bill en masse, the two lawmakers are essential to getting the bill through the evenly divided chamber. The two lawmakers have balked at the price tag of the bill – which would fund major expansions to social safety net programs and provisions to fight climate change – and now face pressure to provide the president a topline number of what they can live with.

“We just have to make difficult choices,” House Speaker Nancy Pelosi, D-Calif., told House Democrats during an evening caucus meeting Monday, according to a person familiar with the private session.

Pelosi told House Democrats that Biden was “working on that piece” – the overall figure for his signature measure – as negotiations were underway with the Senate.

The behind-the-scenes talks come as Republican senators blocked a bill Monday to keep the government operating and allow federal borrowing. Democrats aiming to avert a shutdown pledged to try again — at the same time pressing ahead on Biden’s big plans to reshape government.

The efforts are not necessarily linked, but the fiscal yearend deadline to fund the government past Thursday is bumping up against the Democrats’ desire to make progress on Biden’s expansive $3.5 trillion social spending and climate legislation.

It’s all making for a tumultuous moment for Biden and his party, with consequences certain to shape his presidency and the lawmakers’ political futures.

“You know me, I’m a born optimist,” Biden told reporters Monday, as he rolled up his sleeve for a COVID-19 booster shot. “We’re gonna get it done.”

Monday’s 50-48 vote against taking up the bill fell well short of the 60 needed to proceed over a GOP filibuster. Democratic Majority Leader Chuck Schumer switched his vote to “no,” a procedural step to allow him to bring the measure back for consideration.

With days to go, Democrats said they will try again before Thursday’s deadline to pass a bill funding government operations past the Sept. 30 fiscal year end, stripping out the debate over the debt limit for another day, closer to a separate October deadline.

Meanwhile, the real action is unfolding behind the scenes over the $3.5 trillion measure, with Biden and his Democratic allies in Congress seeking a once-in-a-generation reworking of the nation’s balance sheets.

From free pre-kindergarten and child care subsidies for families with small children to dental care and hearing aids for seniors with Medicare, there’s a lot in the president’s proposal — all to be paid for with higher taxes on corporations and the wealthy.

With Republicans solidly opposed, Democrats are rushing to trim the total and win holdouts within their own party.

As the overall price tag comes down, Pelosi said the House Democrats would not move ahead on a bill until it is acceptable to their colleagues in the Senate. “We’re not there yet,” she said.

Exiting the caucus meeting, Rep. Richard Neal, D-Mass., the chairman of the Way & Means Committee, said as momentum builds toward Thursday, he was expecting a new total amount: “Let’s pop the number.”

Building on a separate $1 trillion bipartisan public works package that’s already cleared the Senate and is heading for a House vote Thursday, Biden is seeking major spending for health care, education and efforts to tackle climate change. The total price tag, he contends, is actually “zero” — covered by the expected increase in tax revenue.

He is personally calling fellow Democrats in Congress an effort to resolve differences and bring his sweeping domestic policy vision forward.

Ticking off the weighty list of goals along with meeting the other deadlines, Biden said, “If we do that, the country’s going to be in great shape.”

But Republicans say it’s real spending that can’t be afforded, and a reflection of the Democrats’ drive to insert government into people’s lives.

And so far, the bill is also too big for key Democrats whose votes are needed in the face of the GOP opposition. Two Democratic holdouts, Sens. Joe Manchin of West Virginia and Kyrsten Sinema of Arizona, have said they won’t support a bill of that size. Manchin has previously proposed spending of $1 trillion to $1.5 trillion.

Progressive lawmakers said they’ve already compromised enough with more centrist Democrats, but in one potential development, Rep. Pramila Jayapal, D-Wash., the chair of the Congressional Progressive Caucus, confirmed she and Sinema have been in talks.

Biden’s proposal is to be paid for by increasing the corporate tax rate, from 21% to 26.5% on businesses earning more than $5 million a year, and raising the top rate on individuals from 37% to 39.6% for those earning more than $400,000 a year, or $450,000 for couples.

While Democrats are largely in agreement on Biden’s vision — many ran their campaigns on the longstanding party priorities — stubborn disputes remain, including how to push toward cleaner energy or to lower prescription drug costs.

With all Republicans opposed, Democratic leaders can’t spare a single vote in the 50-50 Senate, relying on Vice President Kamala Harris to break a tie to pass the eventual package.

All this comes as other deadlines swirl this week to pay for government operations and allow more borrowing or risk a devastating federal shutdown or debt default — though those dire scenarios appear unlikely.

The Associated Press contributed to this report.