NATIONWIDE -- The price of "forever stamps" could again be on the rise as early as January.

The U.S. Postal Service is proposing to increase the price of its first-class stamp by 5 cents to 55 cents.

The price increase — 10 percent — would be the biggest hike since 1991.

Some prices would drop, however.

"The single-piece additional ounce price will be reduced to 15 cents, so a 2-ounce stamped letter, such as a typical wedding invitation, will cost less to mail, decreasing from 71 cents to 70 cents," the USPS said on its website.

If regulators approve the price change, it would take effect January 27.

The Postal Service has struggled for several years with what it called an "unrelenting" drop in mail volume.

It also has faced new competition from online retailers.