WASHINGTON — Speaker Nancy Pelosi of California announced on Sunday that she will call the House back from its annual summer recess for a vote this week on legislation that will block the Postal Service from enforcing any changes to policy that was in place at the start of the year.
The House was not scheduled to return for votes until Sept. 14, but the vote will most likely be on Saturday, according to a senior Democratic aide familiar with the plans. Representative Steny H. Hoyer of Maryland, the majority leader, is expected to announce the final schedule on Monday.
“Lives, livelihoods and the life of our American democracy are under threat from the president,” Ms. Pelosi said in a letter to Democratic lawmakers. “That is why I am calling upon the House to return to session later this week.”
The abrupt return to Washington comes as Democrats called on top Postal Service officials on Sunday to testify on Capitol Hill this month about recent policies that they warned pose “a grave threat to the integrity of the election,” and underscores the growing alarm over changes the Postal Service is enforcing less than three months before a general election in which many Americans will most likely cast their votes by mail. Some of the changes include ending overtime pay or any changes that would delay mail.
It is unclear whether the Senate will take up the legislation, which would require the agency to maintain current service standards until Jan. 1, 2021, or until after the pandemic is over.
Senator Chuck Schumer of New York, the minority leader, said on Sunday that he planned to introduce similar legislation in his chamber. Speaking at an event in New York, he said he would also demand that Senator Mitch McConnell, Republican of Kentucky and the majority leader, bring senators back to Capitol Hill to vote on a similar, stand-alone provision if Ms. Pelosi passed her own version in the House.
The move reflects growing alarm among Democrats and voting rights advocates about changes enacted under Louis DeJoy, the postmaster general and a Trump megadonor, that have resulted in delays in delivery and curtailed service.
They say the changes undermine casting ballots by mail when millions are expected to do so because of the coronavirus if pandemic, pointing to the Postal Service’s decision to tell states that it may not be able to meet their deadlines for delivering last-minute mail-in ballots.
“The postmaster general and top Postal Service leadership must answer to the Congress and the American people as to why they are pushing these dangerous new policies that threaten to silence the voices of millions, just months before the election,” the lawmakers said on Sunday. Mr. DeJoy had been scheduled to appear before the House Oversight Committee in late September, and lawmakers have already requested information about the changes, like cutting overtime and removing mail-sorting machines.
But Ms. Pelosi and Representative Carolyn B. Maloney of New York, the chairwoman of the House Oversight Committee, pressed for Mr. DeJoy and Robert M. Duncan, the chairman of the Postal Service Board of Governors, to testify on Aug. 24. Mr. Schumer and Senator Gary Peters of Michigan, the top Democrat on the Homeland Security Committee, said Senate Democrats had begun investigating the slowdown in mail deliveries. Mr. Peters urged his Republican counterpart, Senator Ron Johnson of Wisconsin, to hold a similar hearing.
The changes under Mr. DeJoy, who has significant financial interests in the Postal Service’s rivals and contractors, in addition to President Trump’s frequent attacks on the agency, have prompted concerns about its politicization. Since his appointment in May, Mr. DeJoy has put in place cost-cutting measures that he says are intended to overhaul an agency beleaguered by billion-dollar losses.
Mr. Trump, for his part, has assailed the service near daily, baselessly claiming that the election could be riddled with fraud if voting by mail is widely used. (He also requested an absentee ballot in Florida, public records show.) He has made clear that he opposes providing additional relief to the agency, though he said he would not veto an economic stimulus package over such funding.
Mark Meadows, the White House chief of staff, claimed on Sunday that no mail-sorting machines would be dismantled before Election Day and insisted that the notion that they would be was a false “political narrative by my Democrat colleagues.”
But Mr. Meadows said that the administration would be open to a measure that would provide supplemental funding to help the Postal Service handle a surge in mail-in ballots.
“The president of the United States is not going to interfere with anybody casting their votes in a legitimate way, whether it’s the post office or anything else,” he said, speaking on CNN’s “State of the Union.”
With lawmakers scheduled to remain scattered across the country through early September, rank-and-file Democrats have pushed leadership to return early and address what they say is a growing crisis before the election in November.
“The delays from the post office are currently the No. 1 issue people are raising with me in person, on our office phones and via mail,” said Representative Elissa Slotkin, Democrat of Michigan, adding that the Oversight Committee “should come back to Washington as soon as possible to hold a public hearing with the postmaster general.”
Representative Jim Cooper, Democrat of Tennessee, declared on Twitter that “we need to subpoena the Postmaster General, and if he fails to appear, we should send the Sgt at Arms to arrest him.”
Protesters in Washington also called over the weekend for the resignation of the postmaster general, saying changes under his purview had jeopardized people’s ability to vote.
About 100 people gathered outside Mr. DeJoy’s apartment complex on Saturday, according to videos posted on social media. Banging spoons on pots, blaring horns and chanting “resign” in the wealthy residential neighborhood of Kalorama, many in the group were wearing masks and maintaining social distance.
Posts on social media also showed protesters delivering fake absentee ballots to the entrance of Mr. DeJoy’s building, cluttering the glass front doors with folded sheets of paper that read, “Save the post office. Save our democracy.”
Aishvarya Kavi and Annie Karni contributed reporting.