A U.S. Postal Service official has alleged that the agency is moving forward with a “secretive, rushed” effort to implement President Trump’s order exerting federal control over mail voting, despite a court order blocking those plans.

The official filed a whistle-blower report, published on Tuesday morning by the office of Senator Richard Blumenthal, Democrat of Connecticut, asserting that the “risky and haphazard” implementation of Mr. Trump’s order could lead to a “catastrophic failure” in the mail ballot system ahead of this year’s midterm elections. The report said that the agency had planned to complete the new digital system overseeing mail ballots by Sept. 1.

“Potentially millions of American voters may not receive their mail-in ballot this election cycle in a timely manner, or at all,” the official said in the report, which was prepared with the assistance of Whistleblower Aid, a nonprofit group that represents people seeking to expose potential lawbreaking.

Speaking to reporters by phone on Monday, Mr. Blumenthal said of the report that “the main takeaway for me is that the Postal Service has designed a system to disenfranchise millions of Americans. One-third of all Americans cast their ballots by mail, and the U.S.P.S. puts all of their votes at risk.”

A Postal Service official declined to comment on the record.

Voting by mail will become much more difficult, if not impossible, for tens of millions of Americans if the Postal Service is allowed to implement the restrictive rules governing mail voting that Mr. Trump has demanded.

Mr. Trump has repeatedly promoted false claims of widespread fraud through mail-in voting, which he has described as “cheating,” “corrupt” and “horrible,” even though he voted by mail in two elections this year. He has moved to restrict mail-in voting using a variety of procedural and legislative levers.

Those moves have led to a pileup of legal rulings and challenges surrounding the nation’s electoral system just two months before the midterm elections. The rules could especially affect states where some of the most competitive races for House, Senate and governor will determine control of Congress and state governments.

Michigan, where 37 percent of votes were cast by mail in 2022, would be one, with competitive statewide contests and multiple battleground House races. California, which mails ballots to all voters, is expected to be central to Democratic efforts to win control in the House.

The Supreme Court had allowed the Trump administration to move ahead with Mr. Trump’s mail ballot executive order, reasoning that a lawsuit challenging the order was premature because the administration had not started implementing its plans.

But days before the court ruled, the Postal Service formally published a new plan to comply with the executive order. Judge Indira Talwani, a Federal District Court judge in Massachusetts, reasoned that the stakes had changed with the new plan and temporarily blocked it, concluding that the agency’s plan appeared to overstep its legal mandate and could spark chaos by changing rules a little more than two months before an election.

The whistle-blower report provided specific details of the Postal Service’s effort to rapidly implement a new digital system for mail ballots, even as a federal appeals court had blocked the plan before the Supreme Court intervened. Work has also continued on the system even after Judge Talwani ordered the plan halted last week, the report said.

The official at the Postal Service raised “grave concerns” in the report that the verification process in the system could reject tens of thousands of ballots in a bulk-mailing batch if “even one bar code on one single ballot” failed to properly scan, and that the rushed, “slapdash” development of the system would significantly increase the chance of errors and other failures in the verification process.

The Brazilian billionaire who shares control of JBS, the world’s largest meatpacker, lobbied President Trump to lower tariffs on beef imports as a way to tame rising U.S. prices.

Joesley Batista met with Trump in the Oval Office on Aug. 20, and they discussed how additional beef supplied from Brazil could help if Trump dropped a 26% import tax, according to people familiar with the matter. It couldn’t be learned who organized the meeting between Batista and Trump.

The next day, on social media, Trump announced a plan to temporarily allow more foreign beef imports into the U.S. Trump said the imported products would be sold at a 25% discount to market prices.

In a statement that day, the Brazilian government said President Luiz Inácio Lula da Silva held an 80-minute call with Trump that touched on issues including tariffs, combating organized crime, and their views on current global conflicts. Brazil is the world’s largest producer of beef.

Rising beef prices have been a vexing conundrum for the Trump administration in its effort to lower costs on everyday goods. By agreeing to lower the tariffs on imported beef and reduce prices for consumers, Trump infuriated ranchers and drew strong rebukes from Republican lawmakers and industry groups. The National Cattlemen’s Beef Association, the largest trade group for cattle ranchers, said government intervention will only hurt ranchers and prevent long-term stability in the beef industry.

Trump’s decision to temporarily lift tariffs on beef were met with pushback from Republicans fighting to win tough elections in the midterms in rural areas. Iowa Rep. Ashley Hinson, the Senate GOP nominee in her state, called the plan a bad idea. Nebraska Sen. Pete Ricketts, who is running for re-election, said on X that “short term policy shifts do not equal long term solutions.”

JBS has played a key role in helping shape Trump administration views, even before the recent executive order. Pilgrim’s Pride, the nation’s second-largest chicken processor, which is majority controlled by JBS, contributed $5 million to Trump’s inauguration, making it the biggest donor.

JBS has said that it has a long history of participating in the civic process and creating opportunities to provide safe, affordable food for American families.

The Justice Department is investigating the top four U.S. meatpackers—including JBS—over whether the companies are engaged in anticompetitive behavior. The companies have denied any wrongdoing and are struggling financially as cattle become more expensive to process in the U.S. Tyson Foods and JBS have closed plants after losing hundreds of millions of dollars processing beef.

For JBS, importing more of its Brazilian product into the U.S. would give the meatpacker a bigger share of the American market. Brazil sent about $1.5 billion worth of beef to the U.S. through the first six months of this year, up 10% from the year prior, according to Agriculture Department data.

JBS began as a family-owned slaughterhouse in the Brazilian countryside. It has since expanded to be one of the largest beef processors in the U.S. and Brazil, employing about 280,000 people in more than 20 countries.

Last year, the company listed its shares on the New York Stock Exchange, a goal it has long sought, hoping to draw a wider pool of investors and cement its image as an American meat giant.

Joesley Batista and his brother Wesley Batista are currently board members and major shareholders of JBS. The brothers were nearly sidelined after a corruption scandal in Brazil almost a decade ago, in which they admitted to bribing politicians and spent several months in jail. They separately settled U.S. corruption charges.

The company has said it now has a robust compliance program and that the brothers bring decades of operational experience.

The import plan from the Trump administration comes in response to a continuing shortage of cattle on American pastures. The supply shortage has driven up livestock prices, and in turn, pushed beef prices to record highs.

Trump’s plan calls for up to 300,000 metric tons of lean beef trimmings to be imported into the U.S. over a 90-day period without a tariff. That total accounts for about 2% of the nation’s annual beef consumption.

A larger supply of lean meat from South America could temporarily lower prices for ground beef sold at grocery stores or found in fast-food restaurants. But it could also discourage ranchers from rebuilding their cattle herds, prolonging the supply shortage, according to analysts.

The announcement helped send cattle prices down, a move that could temper the profits that ranchers make on their animals. Feeder cattle futures, the price ranchers are paid by feedlots, are down about 9% over the past month, according to FactSet.

In May, the Trump administration floated a plan to suspend a tariff-rate quota applied to beef-exporting nations. But the plan was put on hold following an outcry from ranchers, administration officials, including Agriculture Secretary Brooke Rollins, and some congressional Republicans, The Wall Street Journal reported.

The Trump administration has taken several other actions to try to lower beef prices. It has announced plans to provide funding to boost smaller meatpacking operations to boost competition in the sector.

The Agriculture Department said in July it would reopen ports along the U.S.-Mexico border that had been closed to stem the spread of New World screwworm, a flesh-eating parasite. Meatpacking executives have said resuming the cattle trade was the fastest way to potentially lower beef prices.