It will cost more to send mail starting Sunday.
The first rate increase since 2002 will boost the cost of sending a first-class letter within the U.S. by 2 cents, to 39 cents.
The increases will affect all types of mail and packages, including postcards, which will go up by a penny to 24 cents.
The increase follows legislation passed in 2003 requiring the Postal Service to place $3.1 billion in an escrow account this year. Another rate boost is likely next year to cover rising costs.
Postal service spokesman Jim Quirk said Congress was supposed to decide within 180 days after passage of the law what the money would be used for. "Two years have passed and that determination has not yet been put into law," Quirk said.
Without the reserve requirement, a rate hike could have been avoided this year, he said.
The postal service ended its 2005 fiscal year on Sept. 30 with $1.4 billion in net income on operating revenue of $69.9 billion.
The cost to mail an item weighing up to half a pound via Express Mail, the postal service's fastest delivery method, will rise to $14.40 from $13.65.
Priority Mail, which delivers packages in an average of two to three days, will cost $4.05 for packages up to one pound, an increase from $3.85.
International rates will rise by similar amounts. Mailing a letter to Europe or Asia will cost 84 cents, up four cents; a letter to Canada or Mexico will go up three cents to 63 cents.
The price of a regular first-class stamp rose three cents in June 2002.