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The new members' pledge to back the Android software is a significant feat for Google in the mobile phone industry, as its T-Mobile G1 phone takes on rival Apple's wildly popular iPhone 3G.

Sony Ericsson said on Tuesday its support for the the Open Handset Alliance as well as plans to release a mobile phone that uses the Android software in mid-2009.

"Sony Ericsson is excited to announce its membership of the Open Handset Alliance and confirm its intention to develop a handset based on the Android platform," said Rikko Sakaguchi, CVP and head of Creation and Development at Sony Ericsson. "We believe Sony Ericsson can bring a wealth of experience in making consumer focused multimedia handsets with new user experience to the Alliance drawing on the successes of the Walkman and Cyber-shot sub-brands. Sony Ericsson is a strong supporter of open operating systems and we believe the Open Handset Alliance offers an exciting opportunity for a new and unique user experience only Sony Ericsson can deliver."

Membership of the Open Handset Alliance will complement the company?s existing Open OS strategy which is based on the Symbian and Windows Mobile platforms.

"Android is set to become a significant application framework for mobile phones," said Ericsson's head of mobile platforms Robert Puskaric in a statement.

Taiwan's Asustek Computer, Toshiba and Garminalso pledged their support, bringing the total number of companies in the Open Handset Alliance to 47.

Both Google and Apple have wooed developers to create applications for their mobile devices, but Apple keeps a tight grip on the iPhone's hardware and operating software. Google's Android is open to being changed by outside developers.

T-Mobile has already offering its G1 android-based phone made by HTC, while NTT DoCoMo Inc is also expected to bring the first Android phone to the Japanese and South Korean markets next year.