LOS ANGELES - Microsoft unveiled a tablet called Surface on Monday, in a move to rival Apple's massively successful iPad.

The world's largest software maker is on track to launch its touch-friendly Windows 8 operating system this autumn and wants to make a big impact with its own device to kick-start demand.

The tablet will come in two versions, one running on traditional Intel chips and another using ARM microprocessors. Both will have a fold-out cover that becomes a keyboard.

A prototype was demonstrated by Microsoft CEO Steve Ballmer at an event in Los Angeles.

The tablets will be available when Windows 8 ships later this year, according to a Microsoft statement.

No details on pricing were mentioned, except that it would be "comparable" with current ARM tablets and Intel-powered Ultrabooks.

Microsoft shares rose slightly in after-hours trading. They closed down 0,6% at $29,84 in the regular Nasdaq session.

Launching its own tablet potentially throws Microsoft into direct competition with its closest hardware partners such as Samsung Electronics and Hewlett-Packard.

Sales of tablets are expected to triple in the next two years, topping 180-million a year in 2013, easily outpacing growth in traditional PCs. Apple has sold 67-million iPads in two years since launch.

Apple, which makes both hardware and software for greater control over the performance of the final product, has revolutionised mobile markets with its smooth, seamless phones and tablets. Rival Google may experiment with a similar approach after buying phone maker Motorola Mobility this year.

REUTERS