The US Postal Service has halted the controversial policies that were decried as an attempt to sabotage the 2020 election.
Postmaster General Louis DeJoy said he would reverse operational changes that critics say would hamper postal voting.
The U-turn comes as Louis DeJoy is due to testify to Congress and at least 20 states were preparing to sue.
There is a fierce debate over postal funding in 2020, as record numbers of Americans are expected to vote by mail due to the pandemic.
The USPS under Louis DeJoy had begun what it said were cost-cutting measures in recent months.
Policies that were begun under Louis DeJoy included removing mail boxes, cancelling delivery runs and closing down sorting centers.
In a sharp reversal, Louis DeJoy has now said that post office hours would not be cut, and post boxes and sorting machines would stop being removed.
Louis DeJoy, a former Republican donor, also said overtime pay would continue to be approved to ensure deliveries arrive on time.
He said in a statement: “To avoid even the appearance of any impact on election mail, I am suspending these initiatives until after the election is concluded.”
The development comes as the row over the politicization of the most popular US government agency has become a top issue in the 2020 presidential campaign.
Over the weekend, former President Barack Obama – in what was regarded as his most high-profile criticism of President Donald Trump to date – accused his successor of trying to “actively kneecap” the postal service.
Defenders of the changes said they were necessary to help the USPS get out of financial debt. Its budget shortfall has risen to $160 billion amid a decade-long decline in mail volume.
However, Mark Dimondstein, the president of the American Postal Workers Union which represents more than 200,000 postal employees, told Fox News on August 18 that the changes “are truly slowing down mail, the customers see it… the postal workers see it – mail is getting all backed up”.
On August 19, Nancy Pelosi, the Speaker of the House, cheered the postmaster’s volte-face, telling reporters: “They felt the heat and that’s what we were trying to do, make it too hot to handle.”
On August 16, Nancy Pelosi had recalled the House from a recess in order to investigate the USPS policies.
Louis DeJoy, a major political donor who was appointed by President Trump to lead the USPS in May, is due to testify to a Republican-led Senate committee on August 21, and then to a Democrat-led House committee on August 24.
Last week, President Trump said he rejected a funding boost for the USPS to shore up a predicted influx mail-in voting, claiming without evidence that it would lead to voter fraud and help Democrats.
He has also suggested delaying the election, which he does not have the power to do, to stop postal ballots leading to “inaccurate and fraudulent” results.
Voting by mail is not new to the US. According to Reuters, approximately one in every four voters cast ballots by mail in 2016.
Critics say people could vote more than once via absentee ballots and then again in person, though numerous nationwide and state-level studies over the years have found no evidence of widespread fraud.
However, these are rare incidents, and the rate of voting fraud overall in the US is between 0.00004% and 0.0009%, a 2017 study by the Brennan Center for Justice said.