A new law regulating the post office makes it easier to raise rates as long as the agency doesn't exceed the rate of inflation.
Rates are to be adjusted each May.
Customers, however, can buy Forever stamps, which remain valid regardless of any postal rate increase. However, when the rate goes up, so does the price of Forever stamps.
Postal officials say they have printed an additional 1.5 billion 1-cent stamps in anticipation of the demand from people trying to get rid of their 41-cent stamps.
