Sprint Nextel Corp. and Clearwire Corp. said on Thursday they plan to jointly construct a nationwide mobile broadband network in the United States using WiMAX technology, designed to run more than five times faster than current wireless networks at a lower cost.

Sprint Nextel will focus on geographic areas covering about 185 million people, including 75 percent of the people located in the 50 largest markets, while Clearwire will focus on areas covering about 115 million people.

Sprint expects to begin the initial stage of its construction by the end of 2007 and both companies expect to launch commercial service in the first half of 2008.

Sprint has said it expected to invest up to $800 million in 2007 and between $1.5 billion and $2 billion in 2008 relating to the WiMAX network. It did not say if the Clearwire agreement would change its spending plans.

(Reporting by Martinne Geller in New York and Jennifer Robin Raj in Bangalore)