White House officials are closing in on a large spending plan centered on child care, paid family leave and other domestic priorities, according to two people aware of internal discussions. The package could amount to at least $1 trillion of new spending and tax credits, though details remain fluid.

The American Families Plan, the second part of the administration’s Build Back Better agenda, is expected to be unveiled ahead of President Biden’s address to a joint session of Congress on April 28, the people said. It follows the approximately $2 trillion jobs and infrastructure plan that the White House introduced this month and that is just beginning to be debated by Congress.

While details remained in flux, the White House’s newest plan is expected to call for roughly $1 trillion in new spending and approximately $500 billion in new tax credits, according to the people aware of the internal discussions, who spoke on the condition of anonymity to discuss private deliberations. Aides cautioned that the final details of the plan remained unsettled and were subject to change.

The measure is expected to be largely if not fully paid for with new tax increases centered on upper-income Americans and wealthy investors, the people said. The details of those tax measures remained unclear.

“President Biden has already put forward the first part of his historic plan to invest in the strength of America’s economy and families, and he’ll be outlining the second element of that proposal in the coming days,” Michael J. Gwin, a White House spokesman, said in a statement. “The details of that package are still being finalized, so speculation as to its final contents is premature at this point.”

The plan is expected to devote hundreds of billions of dollars to new programs that Biden highlighted during the presidential campaign and that are highly sought by Democrats in Congress. While final numbers had not been determined, the largest efforts are expected to center on roughly $225 billion for child-care funding; $225 billion for paid family and medical leave; $200 billion for universal prekindergarten instruction; hundreds of billions in education funding, including tuition-free community colleges across the country; and other sums for nutritional assistance, the people familiar with the matter said.

The tax-credits section includes an extension of the expanded child tax credit through 2025, the people said. The White House is set to reject pressure from a number of Democratic lawmakers — including Sens. Sherrod Brown (Ohio) and Michael F. Bennet (Colo.), as well as Reps. Suzan DelBene (Wash.) and Rosa L. DeLauro (Conn.) — to make the enhanced child benefit permanent. The expanded child tax credit, which offers families $3,600 per young child and $3,000 per older child, was first approved in the $1.9 trillion relief plan and is set to expire at the end of this year.

Brown, Bennet, and DeLauro said in a statement late Monday: “Congress has an historic opportunity to provide a lifeline to the middle class and to cut child poverty in half on a permanent basis. … Permanent expansion of CTC will continue to be our priority.”

Biden’s infrastructure and jobs plan would be funded by more than $2 trillion in tax increases on corporations. By contrast, as The Washington Post previously reported, the tax increases in the families plan are expected to include higher rates on wealthy Americans and investors, in addition to beefing up enforcement at the Internal Revenue Service. IRS Commissioner Charles Rettig recently told Congress that the United States is losing roughly $1 trillion in unpaid taxes every year in large part because of tax evasion, particularly among the wealthy and corporations.

Taken with the jobs plan, Biden’s spending plans would amount to one of the most significant government transformations of the economy in decades. White House officials and congressional Democrats have not determined whether they will seek to move the jobs and infrastructure first or package it with the other proposal plan and try to pass both at the same time.

Republican opposition to the White House’s newest plan will probably be steeper than the opposition so far to the infrastructure proposal. The GOP is likely to oppose the tax increases and the spending provisions in the newest proposal, whereas Republicans in Congress do support parts of the physical infrastructure investments in the White House’s jobs plan.