Written By Krishanu. On Oct 04. In Social

T-Mobile USA will join AT&T Inc. in selling a smartphone using Microsoft Corp.’s revamped mobile operating system, Windows Phone 7, according to people familiar with the launch plans.

T-Mobile USA will sell a device made by Taiwan-based HTC Corp., a person familiar with the plans said. T-Mobile USA may sell a more business-oriented Windows Phone 7 device later.

Adding another carrier partner gives Microsoft an additional outlet for distribution and boosts its chances for mass adoption of its platform. The Windows Phone 7 software represents Microsoft’s attempt to reinvigorate its ailing mobile business and stay relevant in the area that technology is headed.

AT&T remains the marquee partner in pushing Windows Phone 7 and will launch with the devices initially. Microsoft sent out invitations to its unveiling next Monday, an event that features Microsoft Chief Executive Steve Balmer, as well as Ralph de la Vega, head of AT&T’s consumer and mobility businesses.

T-Mobile USA is scheduled to be at a smaller afternoon meeting at the event. The timing of its phone launch is still in the works, the people said.