The U.S. Postal Service, which is trying to cut $20 billion in operating costs by 2015, is seeking to slow mail delivery to help save $2.1 billion a year.

The agency is asking the Postal Regulatory Commission to let it relax delivery standards for first-class mail, which includes letters and bills, David Williams, vice president of network operations, said today at a news conference in Washington. Ending next-day mail delivery would reduce the number of mail-processing plants the service needs, he said.

The Postal Service said in September it was considering loosening delivery standards and closing 252, or more than half, of its mail-processing plants. The agency said last month it predicts a $14.1 billion loss in 2012 as mail volume continues to drop.