Clearwire has been slowly building up its WiMAX wireless network around the country, starting with small markets and moving to big ones. But with Verizon Wireless almost ready to launch its competing LTE service, which will reportedly reach 38 major urban markets by the end of the year, the company is racing to bring their high-speed wireless services across some of the busiest U.S. cities. Specifically, Sprint has said it plans to launch its WiMAX-based “4G” service in New York City on November 1, followed by Los Angeles on December 1 and in San Francisco by the end of 2010.

The company had already announced last month it was almost ready to begin the rollout in these markets, and offered early adopters a monthly rate of $35 for its 4G/3G+ unlimited mobile Internet plan, which expires in two months and reverts to the standard $55 subscription. The imminent addition of what’s seen as key battlegrounds for U.S. telecom providers will help Sprint fend off Verizon’s LTE assault, though the latter is expected to have the upper hand when it comes to download speeds – offering 5 to 12Mb/s downloads versus WiMAX’s 3 to 6Mb/s.

The high-speed wireless service will be offered by Clearwire under its "Clear" brand and by Sprint, which owns a majority stake in Clearwire. It will also be offered by partners Time Warner Cable in New York and by Comcast in San Francisco.