Amazon.com Inc., the largest online retailer, is opening a store to sell software for the Android mobile-operating system, stepping up rivalry with Google Inc.

This new Amazon app store will supply both Android powered smartphones, as well as Android powered tablets, and there will be an Amazon App store application that you can download directly to your device or tablet.

The retailer is aiming to tap rising demand for games and entertainment that can be downloaded on mobile phones. That market, which is being pursued by more than 30 app stores, may rise to $40 billion by 2014 from $14.3 billion last year, according to Booz & Co. Competitors are trying to grab business from Google’s own Android Market, which has rankled some users for being cumbersome.

The Amazon app store can be downloaded to a phone or tablet computer. Customers can also buy apps on Amazon.com using a one- click option that links back to their Amazon account, rather than entering a credit-card number manually for each purchase.

Applications for Apple Inc.’s iPhone and iPad, which compete with Android-based devices, are available only through Apple’s own app store.