United Online Inc. said it has entered into an agreement with Covad Communications Group Inc. to expand United’s NetZero DSL broadband Internet service to Covad’s network.

San Jose-based Covad sells Internet and telecom service to more than 57 million customers in 44 states.

“Through this agreement, United Online has the opportunity to benefit from access to Covad’s network and their expertise in broadband,” said Mark Goldston, chief executive of United Online. “We believe it will enable us to expand our NetZero DSL broadband offering and give more of our customers who want a broadband experience the ability to easily upgrade from dial-up while keeping their NetZero email address.”

The extended DSL service is expected to launch by the end of the first quarter of 2007 and pricing as well as other terms of services will be released closer to the time of launch. United Online expects that up to 35 percent of current customers will have access to the new high-speed offering.

Shares in Woodland Hills-based United Online were flat at $13.63 in early trading Thursday.