TAIPEI/PALOS VERDES, Calif. - Microsoft Corp showed off a version of its next operating system at technology conferences in Palos Verdes and Taipei, as some PC makers grumbled over restrictions on their involvement in the development of the system.

The world's largest software company is expected to launch the new system, code-named Windows 8 and highlighting touchscreen features optimized for tablet computers, in the next 18 months, as it races to catch up with Apple Inc .

But Microsoft has told chipmakers who want to use the system for tablets to work with only one manufacturer to speed up the delivery, Bloomberg and Dow Jones news reported, sparking worries among some PC vendors that they will be left out.

In demonstrations at the D9 conference in Palos Verdes, California, and the Computex show in Taipei, Microsoft executives showed a starting page that resembles Microsoft's latest phone software, with live 'tiles' manipulated by pressing and swiping the screen.

The demonstration shows Microsoft is making progress toward the new operating system, which it promises will run on a range of hardware devices from traditional PCs to laptops and tablets, using both touchscreen and mouse and keyboard commands.

The company said in Palos Verdes that it was "not out of the game" in tablets, a view backed by some in the industry.

"The fact that it's a year or two years after the iPad doesn't really matter. There is already a lot of built-in infrastructure," Adrian Crisan, Sony's director of engineering for VAIO and Mobile of America, told reporters in Taipei on Thursday.

"Today Apple is first on one thing and Microsoft is first for another and, overall, it's going to be a race and whatever customers will like, they will buy."

Separately on Thursday, US chip maker Qualcomm Inc said it would collaborate with Microsoft on the next version of Windows for its Snapdragon family of processors.