Google has officially unveiled Android, a mobile software platform that is generally referred to as the Google Phone.

An early version of a software development kit is slated for release by next week. The first phones powered by the software are expected to hit the market in the second half of next year.

Android bundles an operating system, middleware, user interface and applications. The platform will be made available under an open source licence.

Phones currently rely on proprietary software such as the Symbian operating system and Windows Mobile. Vendors also are increasingly experimenting with Linux.

The multitude of platforms, however, has caused the market to fragment. Users ordering games or ring-tones, for instance, need to know the model of their phones.

Android aims to create a common platform for the mobile phone similar to the PC, allowing developers to craft applications without interference from device makers or operators.

Those operators and device makers, however, will still be able to customise the platform to add features and their corporate brand.

The platform was developed through the Open Handset Alliance, a new industry body that includes technology and mobile providers as well as operators, such as T-Mobile, Motorola and Texas Instruments. Nokia, the majority shareholder of Symbian, is not part of the alliance.

"This partnership will help unleash the potential of mobile technology for billions of users around the world," said Google chief executive Eric Schmidt.

"A fresh approach to fostering innovation in the mobile industry will help shape a new computing environment that will change the way people access and share information in the future."

Google has been at the centre of mobile rumours ever since the company acquired Android, a company set up by mobile pioneer Andy Rubin.

Fed by an image of an early mock-up, speculation suggested that Google was developing a mobile device that would rival Apple's iPhone and Nokia phones.

"Today's announcement is more ambitious than any single 'Google Phone' that the press has been speculating about over the past few weeks. Our vision is that the powerful platform we're unveiling will power thousands of different phone models," said Schmidt.