T-Mobile USA will deploy its long awaited 3G network to 27 markets by the end of this year, covering two-thirds of its customer base, the company said today.

By mid-October, T-Mobile’s UMTS/HSDPA system is planned for Atlanta, Chicago, Los Angeles, Orlando, Philadelphia, Sacramento, San Francisco and Seattle. By the end of the year, service is planned for Birmingham, Denver, Detroit, Kansas City, Memphis and Tampa.

Service already exists in Austin, Baltimore, Boston, Dallas, Houston, Las Vegas, Miami, Minneapolis, New York (including northern New Jersey and Long Island), Phoenix, Portland, San Antonio and San Diego, the company said. Other, unspecified markets will get coverage next year.

T-Mobile hopes that customers will use the extra bandwidth for technologies such as femtocells and for data services on its new Google Android phone. The company also plans to expand its Wi-Fi services, but did not say how.

The nation’s fourth-largest carrier also announced new backhaul agreements with Bright House Networks, FPL FiberNet, IP Networks and Zayo Bandwidth.  The process of implementing those connections starts next spring and could take up to a year, officials said.