Microsoft has introduced its new operating system for mobile phones, saying the software will run on several devices from different manufacturers competing with the iPhone and the Blackberry.

Windows Mobile 6.5 comes with the official launch of Microsoft's application store, Windows Marketplace for Mobile, and an online data synchronization service called My Phone.

Microsoft said more than 30 new devices running Windows Mobile 6.5 would be available in more than 20 countries by the end of the year. Taiwanese manufacturer HTC released at least three new models running 6.5 on Tuesday in the U.S.

Microsoft chief executive Steve Ballmer debunked rumours that Microsoft would be developing its own smartphone.

The Windows Mobile update is the first since March 2008, when version 6.1 came out. Windows Mobile 6.5 is seen as a minor upgrade, with a completely new version, Windows Mobile 7, expected to come in early 2010.

Windows Marketplace for Mobile, Microsoft's answer to Apple's App Store, currently offers only about 250 applications, including Facebook, MySpace and some game titles, but Microsoft says there is a large backlog of apps awaiting approval.

The iPhone's App Store, launched in July 2008, has more than 85,000 available apps. IPhone users have downloaded two billion apps, as of Sept. 28. Phones running Google's Android OS have more than 10,000 apps available to them, and Palm Pre's App Catalog has about 100 apps.

Besides the Marketphone app store, the 6.5 upgrade offers a more finger-friendly interface, rather than relying on a stylus. The OS also comes with a new browser: Internet Explorer Mobile 6.

The My Phone service will allow users to back up their data "in the cloud," with 200 MB of storage available for free.

My Phone will also allow photos taken on a Windows Phone to be published directly to Facebook and Flickr.