WASHINGTON -- Starting June 30 it'll cost more to keep those cards and letters coming.

The first-class mail rate will rise 3 cents to 37 cents and most other prices will also go up. The new rates were approved in February, and the effective date was announced Tuesday by the Postal Service's board of governors.

At the same time, Postmaster General John Potter repeated his promise that rates won't rise again until at least 2004.

Postal board chairman Robert F. Rider said the June increase will help the agency cope with its current economic problems but "the governors recognize that continual rate increases are not the long-term answer."

The post office said nondenominated stamps valued at the new 37-cent rate will go on sale in mid-June. One will have the U.S. flag, and there will be a four-stamp set with antique toys. There will also be a "makeup rate" stamp, displaying a star, worth 3 cents for use with leftover 34-cent stamps.

The increases affect only domestic mail. The international letter rate of 60 cents for the first ounce to Mexico and Canada and 80 cents to other countries remains unchanged.

Chief Financial Officer Richard J. Strasser said mail volume continues to lag and the post office was $303 million in the red for the second quarter of the year, despite cutting expenditures by $499 million.