WASHINGTON (Reuters) - The price of first-class U.S. mail stamps will rise on Sunday to 73 cents from 68 cents, the latest in a series of price hikes.

The plan, announced in April and approved by the Postal Regulatory Commission in late May, raises overall mailing services product prices by 7.8%. So-called Forever first-class stamps can be used at any time - even after prices rise.

The U.S. Postal Service in November reported a $6.5 billion yearly net loss as first-class mail fell to the lowest volume since 1968. On Sunday, stamp prices will have risen 46% over 2019 when they were 50 cents.

USPS has been aggressively hiking stamp prices as it has lost over $100 billion since 2007. It is in the middle of a 10-year restructuring plan announced in 2021 that aims to eliminate $160 billion in projected losses over the next decade.

USPS is the world's largest delivery operation, handling 123 billion pieces of mail and packages annually. It says it accounts for 44% of the world's mail. 

The agency has said it expects its "new pricing policy to generate $44 billion in additional revenue" by 2031.

First-class mail volume, which fell 6.1% in the 12 months ending Sept. 30, 2023, to 46 billion pieces, is down 53% since 2006 - to the lowest volume since 1968. It is used by most people to send letters and pay bills and is the highest revenue-generating mail class, accounting for $24.5 billion, or 31% of USPS 2023 revenue.

In April 2022, U.S. President Joe Bidensigned legislation providing USPS with about $50 billion in financial relief over a decade.

In May, U.S. Postmaster General Louis DeJoy agreed to pause further planned consolidation of the Postal Service's processing network until at least January after a bipartisan group of senators raised concerns about the impact on mail deliveries.