SAN FRANCISCO: Google is unveiling a small tablet computer bearing its brand Called the Nexus Seven, the tablet will have a screen that measures 7 inches (17.5-centimeters) diagonally, smaller than the nearly 10 inches (25 centimeters) on Apple Inc.'s popular iPad.

That means it's more likely to challenge Amazon.com Inc.'s Kindle Fire, which is also 7 inches.

The Nexus Seven will also be light _ at about 0.75 pound (0.34 kilogram), compared with the Kindle Fire's 0.9 pound (0.41 kilogram). The iPad weighs 1.44 pounds (0.65 kilograms).

The device will ship in mid-July starting at $199 — the same price as the Kindle Fire. By contrast, iPads start at $499. Customers can start ordering it through Google on Wednesday, initially in the U.S., Canada and Australia.

The Nexus Seven will run the next version of Google Inc.'s Android operating system, called Jelly Bean. The tablet is also designed specifically for Google Play, the company's online store for movies, music, games, books and apps. Google said Wednesday that Google Play will now offer movies for sale, rather than only rentals.

Google also announced a home entertainment device called Nexus Q. It sends content from your personal collection or YouTube to your existing TV and speaker systems. You control it through a separate Android phone or tablet.

The Nexus Q, which Google is calling the world's first ''social streaming device,'' will available in July in the U.S. initially and sell for $299.

Google made the announcements during a keynote to open its annual conference in San Francisco for computer programmers. A Google expansion into the tablet market brings another imposing entrant into what is already a battle of tech heavyweights. Last week, Microsoft Corp. announced its own tablet, Surface.

Expected to go on sale this fall, Surface will run on a revamped version of Windows and compete directly with the iPad. Although the tablet carries the Google brand, the machine will be made by AsusTek Computer Inc. Google also recently expanded into the device-making business with its $12.5 billion purchase of Motorola Mobility, but the company has stressed that it intends to continue to rely on Asus and other manufacturers that have embraced Android.

There are already other Android-powered tablets on the market, but none have proven nearly as popular as the iPad or Kindle Fire. That has raised worries at Google as more people rely on tablets to surf the Internet.

If Apple and Amazon establish themselves as the dominant tablet makers, they could set up their operating systems in ways that de-emphasize Google's Internet search engine and other services. Apple develops its own system, while Amazon modifies Android for use in Kindles.

Apple already has announced that the next version of the iPad operating system will abandon Google's digital maps as the built-in navigation system. That shift could cause neighborhood merchants to spend less money advertising on Google.

Earlier Wednesday, Google unveiled a new search tool to help you get the right information at the right time on your mobile device. Called Google Now, the tool will be part of Jelly Bean, which will be available in mid-July. Some devices, including the Galaxy Nexus, will get the upgrade automatically over the air.

With Google Now, if you say ''traffic,'' for example, it will look at your usual commute to work and show you alternative routes if there's a lot of traffic. It will tell you the scores of your favorite sports teams automatically, and it will keep you up to date on flight statuses if you are flying somewhere. You'll have to activate Google Now to start using it. Google Inc. said the Google Now feature will get smarter as you use it more. The feature bears resemblance to the Siri virtual assistant on Apple's iPhone.

Jelly Bean will also come with the ability to share photos by tapping two phones together, using an emerging wireless technology called near-field communications.

Google said there are a million new Android devices activated daily, up from 400,000 a year ago. Google says there's particularly fast growth in emerging markets such as Brazil and India. Android is now the chief rival to the mobile software running Apple's iPhone and iPad.