President Biden will go to the Capitol on Thursday to announce progress on a “framework” agreement for a social safety net and climate change bill that would most likely bolster support for child care and early childhood education while coaxing the economy away from fossil fuels.

Details were still unclear on the precise shape of the package, but people familiar with the president’s plan said he would use a 9 a.m. meeting of the House Democratic Caucus to try to convince liberal members that a final deal was close enough to allow them to support a separate, $1 trillion infrastructure bill that has already passed the Senate.

The emerging deal that he and top Democrats were expected to outline is likely to leave some critical issues unresolved, including how to pay for it. And the components that have been agreed to were considerably more modest than the cradle-to-grave expansion of the safety net initially envisioned for a bill that would have been at least twice as large.

But the provisions expected for young children would offer a significant boost to middle-class families that have struggled for decades with economic uncertainty. And the roughly $500 billion expected to be included for programs to move Americans to electric vehicles and entice utilities away from natural gas and coal would represent by far the largest federal investment in combating climate change.

Democratic leaders were keen to hand the president a victory before he departs for Europe this week. The president planned to attend a climate summit on Sunday in Scotland, where he hoped to point to the deal as evidence of the United States’ commitment to tackling climate change.

They also hoped the agreement would be enough to persuade the House’s most liberal members that Congress was on the verge of passing a truly progressive package — and that those liberals, in turn, would join more moderate and conservative Democrats to send the $1 trillion bipartisan infrastructure bill to Mr. Biden for his signature and a much-needed boost for his party.

The extremely close governor’s race in Virginia was another motivating factor, according to two House members. The Democratic candidate, the former Governor Terry McAuliffe, would like to spend the last days of the campaign barnstorming the state to show where new projects will be built.

Liberal members of the House and Senate will likely have plenty to lament. The centerpiece of Mr. Biden’s climate change policy — a measure to reward utilities for switching to renewable energy and to punish those that won’t — was stripped out at the insistence of Senator Joe Manchin III, the Democratic centrist from West Virginia. One of the biggest social policies in the original package, a $500 billion federal paid family and medical leave benefit, is also likely to go.

The promise of two years of free community college will go unfulfilled, and the expanded child tax credit, passed in March to give most families a $300-per-child income support, is expected to be extended only into 2023, not made permanent.

Other measures remain unresolved, including a widening of Medicare benefits to cover hearing, vision and dental care and an extension of health insurance into the 12 states that have refused to expand Medicaid under the Affordable Care Act.

But Speaker Nancy Pelosi of California has said repeatedly that the final social policy measure will be “for the children,” and she will likely be able to claim she fulfilled that pledge. Under the expected agreement, most families would receive six years of assistance with child care costs, ensuring that only a small percentage of their total income is devoted to nursery care.

Universal prekindergarten benefits would last even longer, effectively extending public school downward to age 3. For older Americans, the framework is expected to include several years of community and home health care.

It also contains substantial sums for rental assistance, home-buying help, public housing repair and other affordable housing programs.

“We have the biggest investment in housing since the New Deal,” said Representative Pramila Jayapal of Washington, who heads the House Progressive Caucus. “There’s a lot of really good things in this bill, but we have to finish it, and we also have to vote it through.”