Biden to detail core elements of $1.75 trillion economic and climate package in effort to jumpstart action on the Hill

(CNN)President Joe Biden will lay out long-awaited details of his $1.75 trillion economic and climate package to House Democrats on Thursday when he attends a caucus meeting on Capitol Hill as leaders press progressives to vote for a $1 trillion bipartisan infrastructure bill.

While the 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.