Sprint announced a soft launch of its WiMAX services is underway in three major U.S. cities as a trial run to prepare the technology for wider launch later this year.

Xohm, which serves as Sprint’s high-speed wireless Internet division, will begin offering mobile Internet business agreements for both Web portal services and WiMAX network access starting Tuesday, the company announced. The WiMAX mobile Internet services will be available in Chicago, Baltimore and Washington, D.C., the company says, with plans to have a broader commercial launch of the technology later this year. Xohm says that its goal for WiMAX is to eventually “mobilize the Internet, bring wireless innovation to devices and deliver new mobile multimedia applications to consumers, businesses and local governments.”

“Sprint is delivering on its open Internet vision with exciting and differentiated WiMAX services,” says Barry West, the president of Xohm’s business unit. “The new service agreements and device commitments will help Xohm subscribers access, enjoy, store and secure personal digital and user-generated content while experiencing new device innovation.”

Sprint’s launch of WiMAX comes during a troubled time for the carrier, which only weeks ago named former Embarq chief Dan Hesse as its new CEO. In recent years, Sprint has experienced continued difficulties in integrating former Nextel users into the Sprint network; investor nervousness over the future of its $5 billion WiMAX investment; and a shrinking subscriber base.

Late last year, interim Sprint CEO Paul Saleh suggested that the company could spin off its WiMAX division to concentrate more fully on customer service and on improving its basic wireless offerings. In December of last year, Sprint announced it had terminated its letter of intent to build out a nationwide WiMAX network with Clearwire.

But despite uncertainty over its future WiMAX plans, Sprint has consistently maintained that it was committed to soft-launching the technology in early 2008 with the goal of giving it a broader launch by the end of the year. Philip Solis, a principal analyst for mobile broadband at ABI Research, said last year that Sprint’s scheduled 2008 WiMAX rollout could put it ahead of its competitors in delivering high-speed mobile broadband and could help differentiate the carrier from AT&T and Verizon.