Pelosi declares infrastructure bill on track, setting up a showdown between her party’s feuding factions.

Speaker Nancy Pelosi on Thursday vowed to push ahead with a House vote on a $1 trillion infrastructure bill that passed the Senate with bipartisan support, driving Democrats toward a showdown between moderate supporters of the bill and liberals who have said they will bring it down without progress on a separate social policy measure.

Democratic leaders told lawmakers that no votes would occur before 9 p.m., but did not rule out the possibility of completing work on the bipartisan bill Thursday evening.

Democrats entered Thursday juggling four consequential tasks on the final day of the current fiscal year: keeping the government open past midnight, ensuring it can pay its debts, securing the infrastructure bill and drafting a climate change and social safety net bill that the speaker called the “culmination” of her congressional career.

They accomplished the first task, as both the House and Senate managed to pass a bill to keep funding flowing into early December, removing the immediate threat of a government shutdown.

The rest is a mess. Liberal House members emerged from a meeting with the speaker at midday to say they would oppose passage of the infrastructure bill until the Senate pass a $3.5 trillion social policy bill that expands child care and early childhood education, creates a paid family and medical leave program and begins to tackle climate change, to name only a few provisions.

“The speaker really just wanted to see where we were, and we explained that we’re in the same place,” said Representative Pramila Jayapal, Democrat of Washington and the head of the Congressional Progressive Caucus.

But Senator Joe Manchin III, Democrat of West Virginia, told reporters he has no intention of voting for any social policy and climate change bill that costs more than $1.5 trillion over 10 years. His advice for Democrats who want a larger package: “Elect more liberals.”

Ms. Pelosi, speaking at her weekly news conference, stayed relentlessly optimistic, speaking of the common ground she shares with Mr. Manchin, a fellow Italian American and Catholic.

“Let me tell you about negotiating: You cannot tire,” she said.

Both the infrastructure and social policy bills are major priorities for President Biden, who invested ample political capital in the infrastructure compromise and has staked his presidency on enactment of a transformational social policy package.

White House officials declined to discuss the details of meetings and discussions with Mr. Manchin and the other Democratic hold out on the $3.5 trillion package, Senator Kyrsten Sinema of Arizona, which have intensified in recent days as some Democrats have grumbled that the president needed to play a bigger role in ensuring the success of his agenda.

Andrew Bates, a spokesman for the White House, rejected the criticism, saying Mr. Biden was doing precisely what he needed to.

“He knows how to make his case, he knows how to count votes, and he knows how to deliver for the American middle class,” Mr. Bates said.

But it was unclear, with Republican leaders in the House urging their members to oppose the bipartisan infrastructure bill, whether the legislation could overcome liberal defections on Thursday.