Microsoft reportedly plans to unveil the first smartphones running Windows Phone 7 on October 11.
The software giant will reveal smartphones made by Samsung, LG and HTC and announce an initial exclusive handset partnership with US carrier AT&T, internal sources told the Wall Street Journal.
AT&T plans to start selling the devices on November 8, the sources said, but the first units could be in stores from October 21, All Things Digital reported.
The news site said Microsoft has signed another exclusive carrier partnership with Orange.
Microsoft opened registration for developers looking to embed mobile adverts in their applications on Wednesday.
An applications software development kit for the new OS was launched last month.
The software firm is banking on the OS to halt the erosion of its market share by competitors including Apple and Google. Microsoft's share of the smartphone OS market nearly halved to 5% in Q2 from 9.6% the year before, according to Gartner.
Its slice of the market is down significantly from the 11.5% share it held around the time of the first iPhone's launch in 2007.
An attempt to address the declines with the launch of the Microsoft-branded Kin failed – Microsoft pulled the plug after poor sales of the youth-centric smartphone.
The open-source Android platform has so far proved more enticing to handset manufacturers and developers than Windows Phone's closed-garden approach.
Microsoft chief Steve Ballmer in June admitted the company had missed out on an entire cycle of the handset industry, but said that leadership changes within the Windows Phone software group should aid a turnaround.