Corrects sixth paragraph to reflect that Sony had earliest e-reader launch, not Amazon

SAN FRANCISCO - Top U.S. bookseller Barnes & Noble Inc announced on Monday the launch of the world's largest online bookstore, with over 700,000 titles that can be read on a range of platforms from Apple's iPhone to personal computers.

Sounding a challenge to online retailer Amazon, the company said its selection would grow to over 1 million titles within the next year and include every available e-book from every book publisher.

Barnes & Noble also said it will be the exclusive provider of digital books on the Plastic Logic e-reader, a device expected to compete with Amazon's Kindle and due to launch early next year. now offers more than 300,000 electronic book titles, available only to users of its Kindle device.

Barnes & Noble's full-fledged foray into the digital book arena comes as a host of companies jockey for position in the emerging but fast-growing industry.

Amazon's launch of the Kindle in 2007 was the highest-profile launch of an e-reader, but other companies, including Japan's Sony Corp -- which beat the Kindle to market by over a year with its own digital reader -- have come out with their own versions.

(Reporting by Alexandria Sage; Editing by Tim Dobbyn)