The plan includes closing 252 of its 487 mail processing facilities. With these closures, first-class mail will move to a two-to-three day standard delivery time and next-day delivery will be rare.
The plant closures are expected to result in the elimination of roughly 28,000 jobs nationwide, according to the Associated Press.
The Postal Service says the change, part of its network optimization initiative, will save $3 billion by 2015.
The move will not solve financial troubles at USPS, which lost $5.1 billion in fiscal 2011. According to David Williams, vice president of network operations, USPS must reduce operating costs by $20 billion by 2015 to become profitable.
Congress recently decided to defer USPS' $5.5 billion prepayment to its retirees' health benefits, but Joseph Corbett, the Postal Service's chief financial officer, predicted the agency still could run out of money by the end of fiscal 2012.
Sen. Tom Caper, D-Del., chairman of the Senate subcommittee that oversees the Postal Service, lamented Monday's news of closures.
"Today's announcement is another grim reminder that we must act quickly if we want to save the Postal Service and the 8 million jobs that rely on it," Carper said in a statement. "The few measures that the Postal Service can adopt on its own -- such as closing distribution centers and slowing down first-class mail delivery times -- to extend its survival and avoid insolvency will also potentially further erode its declining business."
In addition, Carper touted the bipartisan legislation he sponsored and called for congressional and administrative support for the bill.
The next steps to closing the processing facilities involve the Postal Service's requesting an advisory opinion from the Postal Regulatory Commission and then publishing a notice in the Federal Register, where the public can comment on the proposed changes.