The price to send a first-class letter will increase to 41 cents on Monday.
David Partenheimer, a spokesman with the U.S. Postal Service, said postage is increased to help adjust for inflation, and typically covers the postal service's operating expenses, such as the costs associated with fuel and employee benefits.
Partenheimer said the USPS introduced the Forever stamp last month.
The stamp can be purchased for 41 cents, and retains its first-class value regardless of future postage rate increases, he said.
The price of stamps last increased in January 2006, when it was increased from 37 cents to 39 cents.