Originally Published: 28 OCT 21 05:17 ET

Updated: 28 OCT 21 10:34 ET

By Clare Foran, Daniella Diaz, Phil Mattingly and Kevin Liptak, CNN

(CNN) -- President Joe Biden's legislative agenda hangs in the balance as he pitches a multi-trillion-dollar plan to Capitol Hill in an attempt to bring together progressives and moderates ahead of the President's overseas trip scheduled to begin in just a few hours.

At a closed-door meeting of House Democrats on Thursday morning, Biden laid out in person long-awaited details of his $1.75 trillion economic and climate package, trying to convince progressives who are skeptical of anything short of a fully written bill and commitments from all 50 members of the Senate Democratic caucus to back his framework.

Top Democrats are also hoping the announcement of a framework will be enough to get progressives to vote to pass a separate bipartisan infrastructure bill, but so far that appears doubtful at best.

While Democratic negotiations are expected to continue, failing to seal the deal Thursday and secure an infrastructure vote in the House would be a blow to Biden's administration as well as for his party, which is eager for a win and to prove to voters it can deliver.

Biden departed the meeting after about an hour joined by Speaker Nancy Pelosi and other aides. He waved to reporters but did not respond to shouted questions about his $1.75 trillion infrastructure framework.

Democratic Rep. Alexandria Ocasio-Cortez of New York told reporters Thursday morning ahead of the meeting that progressives need certainty and more than just a framework on the social safety net package to be able to support the infrastructure bill.

"I think we need something a little bit more than just something on the back of an envelope," Ocasio-Cortez said. "I think legislative text is one mechanism of us getting there."

While Biden's proposal isn't finalized in its entirety, days of negotiations have brought it to a place where the key elements are all locked in and Biden plans to impress upon Democrats the scope and scale of what those elements represent, even in the face of several Democratic priorities being dropped from the bill in the last several days.

The White House was expected to lay out specifics of the plan later Thursday morning, and even many Democrats remained in the dark about the exact contours of the agreement in the hours ahead of its unveiling.

"The President will speak to the House Democratic Caucus this morning to provide an update about the Build Back Better agenda and the bipartisan infrastructure deal. Before departing for his foreign trip, he will return to the White House and speak to the American people about the path forward for his economic agenda and the next steps to getting it done," a White House official said.

Biden and Democratic leaders have made clear they want an agreement on the economic and climate package that would clear the way for the House the $1.2 trillion bipartisan infrastructure bill that marks the second of the two pieces of Biden's sweeping domestic agenda.

But House progressives have been explicit that they need to see more than a framework agreement in order to move forward with the infrastructure bill, creating a challenge for any movement unless they move off their position. Not all Democrats have signed off on the framework that Biden will announce Thursday morning, two people familiar with the plan cautioned, but the President believes it's a consensus all Democrats should be able to support.

One source familiar with progressive thinking told CNN that a loose framework is not likely to be enough to convince progressives to vote for a bipartisan infrastructure bill.

The source told CNN that "we are told the two senators have loosely said OK to a very general broad framework, but that they will not yet commit to voting for the bill and that there are still open questions on various pieces."

"This is exactly why we need legislative text and all parties fully agreed to that bill text," the source said.

The stakes are enormous, with Biden making clear privately for more than a week he wants an agreement and passage of the infrastructure bill before he arrives at the UN Climate Conference on November 1. Biden departs for his foreign trip later Thursday, with White House officials moving back his expected departure time in order for him to share details with House Democrats.

Biden's personal pitch to House Democrats, which White House officials and Democratic leaders have been weighing for several days, will be followed by remarks laying out those details to the public. It marks a concerted and concrete effort to wrest control of an unwieldy process that has led to significant revisions to Democratic goals in the effort to secure the support of centrist Sens. Joe Manchin of West Virginia and Kyrsten Sinema of Arizona.

But it also represents a risk should progressive Democrats not accept what he lays out as enough to move forward.

Biden plans to tell House Democrats that he trusts that Manchin and Sinema will vote for the larger social safety net package -- and that he takes them at their word and they should too, a person briefed on the matter said.

But there are up to 55 House progressives who are against the infrastructure bill right now, with many of them demanding passage of the larger bill first or at least the release of detailed bill text, not just a framework, the person said.

House Democrats are huddling at 9 a.m. ET "in person" to discuss the Democratic "Build Back Better" agenda, according to a notice sent to members. In a sign of the meeting's sensitivity, lawmakers will not be allowed to use their phones to prevent details from leaking to the press.

Biden to delay departure for Europe

Although Biden had been scheduled to leave for Europe for the Group of 20 Summit early in the morning, the White House was making plans Wednesday night to delay his departure by a few hours.

Biden's foreign trip is a major moment on the world stage for the President, and the White House has been hoping he would at least have a framework agreement on the spending plan in hand ahead of his departure. But there are still key aspects of a potential deal that remain unresolved, including the overall price tag and how it will be paid for.

Although House progressives want the infrastructure bill and the larger social safety net package to move in tandem, House leadership has continued to push for a vote as early as Thursday on the infrastructure bill, even though it is not clear the votes would be there among progressives.

Democratic Rep. Pramila Jayapal of Washington state, the head of the Congressional Progressive Caucus, on Wednesday said, "I don't think so," when asked if Biden could change her position against voting down the infrastructure bill if it comes up Thursday with the larger bill still unfinished.

House Speaker Nancy Pelosi said on Wednesday that Democrats are "close to agreement" on the larger spending package and announced that the Rules Committee will meet on Thursday in a bid to show forward momentum.

That does not mean an agreement will be ready by that time, however, and it is not yet clear exactly what will happen when the committee meets.

If there is no deal and no bill text by Thursday, the committee may take witness testimony on the proposed legislation in an effort to show progress, even if they are still negotiating the policy and don't have a bill yet.

Contours of a deal emerge

While nothing is finalized and key sticking points remain, the contours of a potential deal are beginning to emerge.

Pelosi on Wednesday outlined the priorities that Democrats have coalesced behind.

In a letter to fellow Democrats, the speaker said there is "broad agreement" for universal pre-K and child care, the child tax credit, home health care, workforce development and housing. She also said "great progress has been made" to address gaps in Medicaid coverage at the state level and "we are pleased" with the climate provisions.

But the speaker wrote that "we are still fighting for a paid family and medical leave provision."

Democrats are now expected to scrap paid leave, discarding one of the central planks of Biden's proposal as they scramble to strike a deal with holdout senators, according to multiple people familiar with the talks.

The plan's survival had been in question for several days due to objections from Manchin.

It's also unclear how Democrats will pay for the plan and whether a proposed tax on billionaires will be part of that.

Amid resistance from Manchin and another Senate Democrat, Virginia's Mark Warner, over the billionaire tax, Democrats are once again scrambling over ways to pay for the plan. Sen. Elizabeth Warren, a Massachusetts Democrats, said on Wednesday that talks were "ongoing" with Manchin to ease his concerns.

Manchin has also expressed concern over an expansion of Medicare to cover hearing, dental and vision benefits, another key priority for progressives.

Senate Democrats cannot afford to lose a single vote to pass the bill under a process known as budget reconciliation. That dynamic has given every single member -- and in particular, moderates like Manchin who have pushed back on a number of the original proposals for the package -- an outsized influence over the process.

This story and headline have been updated with additional developments Thursday.