Democrats in Congress are preparing to vote on legislation to prevent President Donald Trump from scaling back operations at the U.S. Postal Service, but at least a dozen high-capacity mail sorting machines have already been removed from Massachusetts as part of a USPS reduction plan, two officials with the American Postal Workers Union told WGBH News Monday.

The equipment withdrawal, coupled with the seemingly sudden, wide-spread removal of USPS public mailboxes and new overtime and mail delivery policies, are causing national and local outcry from postal workers, politicians and voting rights groups concerned that processing centers may not be able to handle a flood of mail-in ballots in November.

“It’s disturbing to see the machinery taken out,” said Scott Hoffman, APWU Boston Local 100 president. Hoffman said nine machines have been removed from Boston’s Dorchester Avenue post office located downtown.

“When you eliminate machinery, you’re eliminating future possibilities to handle certain fluctuating volumes,” he said pointing to the annual busy periods of tax season, Mother’s Day and Christmas.

John Flattery, president of APWU Central Mass Local confirmed to WGBH News Monday that three pieces of sorting equipment were recently removed from his union’s region, which includes Ashburnham, near the New Hampshire border through Worcester, Franklin, and Sturbridge.

Bill Thomas, another Boston union officer and postal clerk said he believes the changes are a deliberate attempt to undermine the postal service.

“It’s intentionally delaying the mail,” Thomas said in an interview with WGBH News.

The new directives include tamping down overtime and leaving mail behind at processing plants when sorting runs late.

"Before, the truck would wait for the mail from the plant to bring to the stations,” Thomas said referring to large delivery trucks that bring mail from processing centers.

“Now, if the mail is running late on the machine, the truck leaves, that mail's not getting out for the day."

The extent of the local delays and reduced sorting capacity remains unclear.

Documents obtained by WGBH News show a schedule to remove a total of 19 pieces of mail sorting equipment throughout Greater Boston — which includes Providence, R.I. — between the months of June and August. The documents, circulated in June, came along with letters from the Postal Service headquarters in Washington, D.C., that described the move as a response to low mail quantity.

“As a result of the reduction in letter and flat mail volume, the Postal Service is planning to reduce the number of Advanced Facer Canceler Systems, (AFCS), Delivery Bar Code Sorter (DBCS), Automated Flat Sorting Machines 100s (AFSMs) and Flat Sequencing Systems (FSS) in its mail processing facilities,” said a letter addressed to APWU national president Mark Dimondstein.

The various machines, which sort mail parcels for distribution, would all contribute to sorting ballots from voters who elect to cast their votes by mail, according to postal workers.

It is unclear whether the removed machines will be replaced. The Postal Service has not responded to WGBH News requests for comments.

In an interview on CNN Sunday, White House Chief of Staff Mark Meadows first denied that machines were being dismantled, then vowed that no additional sorting machines would be taken offline between now and election day.

Hoffman, a 32-year veteran of the postal service, told WGBH News he views the changes as an “all-out attack” on the postal service by Postmaster General Louis DeJoy, a donor turned Trump-appointee who took the helm of the postal service in June.

“With an edict from up top, they've changed it all. They haven't changed the statutes. They haven't changed the rules and regulations. The only difference is a new postmaster with a new set of edicts,” Hoffman said.