Sprint has announced the launch of Sprint 4G mobile broadband in a number of markets in the U.S., essentially pro forma notifications given that its Clearwire subsidiary – through which Sprint is providing 4G WiMAX – has previously announced service in all of them.

Sprint 4G, aka Clearwire’s Clear WiMAX, is now available in Chicago and in the Dallas-Ft. Worth area . It is also available throughout the Piedmont Triad region in North Carolina – Greensboro, Winston-Salem and High Point – as well as in Charlotte, Raleigh, Durham, Chapel Hill and Cary (all in North Carolina).

Clearwire started selling the service yesterday in Chicago, according to reports from the Chicago Tribune, with Sprint announcing today that mobile WiMAX also would be available under its own brand. Comcast will begin reselling the service later this fall.

Separately, Sprint unveiled a new netbook from Dell that it will be reselling for use on its 3G network.

The Dell Inspiron Mini 10 is the first netbook available from Sprint, the company said. It is now available at select Sprint stores throughout the Bay Area for $199.99 with activation on a Sprint Mobile Broadband plan and a two-year service agreement, after a $100 mail-in rebate. The Mobile Broadband Connection Plan offers 5 GB of data for $59.99 per month.

Sprint said its EVDO Rev A (3G) network provides download speeds between 600 kbps and 1.4 Mbps and upload speeds of 350-500 kbps. Peak download data rates increase to 3.1 Mbps (from 2.4 Mbps), and peak upload data rates increase to 1.8 Mbps (from 153 kbps).

Sprint is struggling to cap widening losses, a problematic churn rate and customer defection. Last week, the carrier said it lost $478 million in its third quarter on a 9 percent drop in sales. Sprint’s churn rate hit 2.17 percent, and it lost 135,000 subscribers.

– Wireless Week’s Maisie Ramsay contributed to this report