Sony cut the size and weight of all three of its ereaders while expanding the use of touchscreens to all models - allowing users to turn pages with a swipe of the finger like the Apple iPad.

The Japanese electronics giant increased the price of its cheapest e-reader, the Reader Pocket Edition, by $US29 ($32) while adding a touchscreen.

At $US179 ($200), the Reader Pocket Edition, which features a four-centimetre screen, is $US40 ($45) more than Amazon's cheapest Kindle e-reader and $US30 ($33) more than US bookstore chain Barnes & Noble's device, the Nook.

The cheapest iPad costs $US499 ($560) but boasts a colour screen and other features, while the Sony Reader and the Kindle both use black-and-white e-ink technology.

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The new Reader Touch Edition features a four-centimetre touchscreen and costs $US29 ($323), while the new Reader Daily Edition has a five-centimetre touchscreen, Wi-Fi or 3G connectivity and costs $US299($336).

Steve Haber, president of Sony's Digital Reading Business Division, said the company was also targeting "previously untapped markets".

"We take a thoughtful approach to country expansion, including Italy, Spain, Australia, Japan and China, working with local bookstores to ensure content is compatible, relevant and in the appropriate language for each market," he said.

Sony also said it was developing applications for the iPhone and Android mobile platform to allow users to read books from its Reader Store on those devices.

Sony said the new Reader Pocket Edition and new Reader Touch Edition are available immediately, while the new Reader Daily Edition will be out in time for end-of-the-year holidays.

Amazon unveiled two new versions of the Kindle in late July, including one that sells for $US139 ($156), its lowest price yet.

Staples announced yesterday it will begin selling the Kindle this year, making the US office supply chain the second brick-and-mortar store to offer the device after retail giant Target.