Letter carriers load mail trucks for deliveries in July at a U.S. Postal Service facility in McLean, Va. One of the unions representing postal workers, the National Association of Letter Carriers representing 300,000 current and retired workers, has endorsed Democrat Joe Biden for president.

WASHINGTON — A major union representing U.S. postal workers has endorsed Democrat Joe Biden for president, a move that comes as President Donald Trump has acknowledged starving the postal service of money in order to make it more difficult to vote by mail in November’s election.

The National Association of Letter Carriers, which represents 300,000 current and retired workers, said Thursday that Trump has long been hostile to the Post Office. His administration has called for an end to collective bargaining rights, proposed service cuts and has eyed the possibility of privatizing the functions of the agency.

But those actions have escalated since the start of the pandemic, with the administration taking “steps outside of the public eye to undermine the Postal Service and letter carriers,” said union President Fredric Rolando.

Biden, on the other hand, “is, was, and will continue to be a fierce ally and defender of the United States Postal Service,” Rolando said in a statement announcing the endorsement of the former vice president and his running mate, Kamala Harris.

Trump has repeatedly railed against the suggestion that more people should vote by mail as a result of the pandemic, which he argues without offering evidence will lead to widespread voter fraud.

The agency’s new leader, Postmaster General Louis DeJoy, a former supply-chain CEO and a major donor to Trump and other Republicans, has pushed cost-cutting measures to eliminate overtime pay and hold mail until the next day if postal distribution centers are running late.

In an interview on Fox Business Network, Trump explicitly noted two funding provisions that Democrats are seeking in a coronavirus relief package that has stalled on Capitol Hill. Without the additional money, he said, the Postal Service won’t have the resources to handle a flood of ballots from voters who are seeking to avoid polling places during the coronavirus pandemic.

“If we don’t make a deal, that means they don’t get the money,” Trump told host Maria Bartiromo. “That means they can’t have universal mail-in voting; they just can’t have it.”