Currently, individual stamps can be printed using computer software supplied by private vendors. That process was introduced in 1999 and the post office said there are currently 390,000 registered customers.

The new system will allow printing of sheets of 25 stamps at a time which can be stored for future use. The stamps can be printed in any needed denomination.

Stamps.com, based in Santa Monica, Calif., is the first company approved to offer the service, called NetStamps. It will supply the software and stamp printing service, the post office said.

The stamps must be printed on special sheets of adhesive-backed label paper which contains watermarks.

Stamps.com said the software and paper will be available immediately with the paper costing $3.99 for a pack of 125 labels. The company charges a monthly fee for the service, in addition to the cost of the stamps.

The Postal Service said computer printing of postage has become particularly popular with small and mid-size businesses, making postage available at any time and providing automatic accounting of mailing expenses.

On the Net:

U.S.Postal Service: http://www.usps.com

NetStamps: http://www.stamps.com/netstamps