By taking a greater role in the tablet arena, Google hopes to ensure that its online services remain at the forefront for consumers, as tablets increasingly become gateways to the Web and Web-based content such as movies and music.

Sales of the 7-inch 16-gigabyte tablet began on the Google Play website on Tuesday with a starting price of 19,800 yen ($250). The device will be available in retail stores from October 2.

Japan is the first country in Asia outside Australia to sell the device. According to the Google Play page it's already available in France, Germany, Spain, Canada, the UK and the U.S.

Google's Android operating system on smartphones and devices now has over 500 million users, Google Executive Chairman Eric Schmidt said, adding that he predicts that growth in the smartphone market will lead to a boom in new startups around shopping in Japan.

"It is the defining platform and the defining battle in our industry," Schmidt said at a briefing in Tokyo.

The tablet market is dominated by Apple Corp and its iPad, which represented about 70 percent of global sales in the second-quarter, and includes Amazon.com Inc's Kindle, Barnes & Noble Inc's Nook and Samsung Electronic' s Galaxy Tab.

(Reporting by James Topham, Kevin Krolicki; Editing by Chang-Ran Kim and Muralikumar Anantharaman)

(This story was corrected to change megabit to gigabyte in third paragraph)

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