Here are the key issues facing Congress today.

Pressing for a quick vote on the bill, nine conservative-leaning Democrats in the House threatened to withhold their votes for the party’s $3.5 trillion budget blueprint until the Senate-passed infrastructure bill cleared their chamber. But now liberals in the House are threatening to withhold their votes for the infrastructure measure until the budget blueprint has successfully made its way through reconciliation.

Democrats’ exceedingly ambitious social policy bill, which Mr. Biden calls his “Build Back Better” plan, is packed with longstanding party priorities. The House has drafted a 2,465-page version that includes a huge array of programs to combat climate change, the extension of a generous child tax credit, universal prekindergarten, greatly expanded access to community college, increased resources for elder care and paid leave, and a Medicare expansion to cover vision, hearing and dental care — all paid for by trillions of dollars in tax increases on corporations and the wealthy.

Speaker Nancy Pelosi had hoped to put it to a vote this week, but she faced two problems: As of now, Democrats most likely do not have the votes, and Senate Democratic leaders have yet to produce a detailed bill that can draw the support of every member of their caucus.

Several conservative-leaning Democrats in both chambers, including Senators Joe Manchin III of West Virginia and Kyrsten Sinema of Arizona, have said they cannot support the plan as proposed. And because Republicans have made it clear they are unified in their opposition, Democrats cannot afford to lose even one vote from their party in the Senate and can afford to lose as few as three votes in the House.

Mr. Biden has been negotiating with the holdouts to determine what they could support. But for now, the lack of agreement on the sprawling plan is blocking its progress — and leaving the fate of the infrastructure measure uncertain as well.