Office supplies retailer Staples Inc will begin selling Inc's Kindle, the latest deal that will expand the availability of the e-reader at retail locations.

Staples will start selling the devices at its more than 1,500 U.S. stores starting in the autumn, the company said on Tuesday. It plans to sell the $139 version of the Kindle, the 3G model and the more expensive Kindle DX.

Amazon, the world's largest online retailer, has sought to make its Kindle available at more stores as it competes with devices such as Barnes & Noble Inc's Nook and Apple Inc's iPad to win a larger share of the growing digital books market.

In April, Target Corp reached a deal to start selling the Kindle in its stores, while electronics retailer Best Buy Co Inc said it would sell the Nook at its 1,070 stores.

Forrester Research estimates that Amazon has sold about 5 million Kindles since the product's launch in 2007, and that Barnes & Noble has sold 1 million Nooks since it introduced the device last year.

(Reporting by Phil Wahba; editing by John Wallace)