Google Inc. (Nasdaq: GOOG) is upgrading Chromebook laptops with faster speeds and a new user interface that’s more reminiscent of traditional personal computers as the company steps up its efforts to take on Apple Inc. (Nasdaq: AAPL) and Microsoft Corp. (Nasdaq: MSFT).

The laptops made by Samsung Electronics Co. will let users navigate Web-based applications more easily by providing tools for accessing Gmail or other software outside the browser, said Sundar Pichai, a senior vice president at Mountain View, California-based Google. The devices, which use faster Intel Corp. chips, are about three times as quick as the first generation of Chromebooks, he said.

“It’s a journey for us, but we’re committed to it for the long run,” Pichai said. “It’s a big jump forward.”

Google, already competing in the market for smartphones with its Android software, is trying to woo consumers and businesses with Web-centric laptops while challenging Microsoft and Apple. Google announced Chrome OS software in 2009 and manufacturers that include Acer Inc. began offering the computers last June.

The latest Chromebooks include a bar across the bottom of the screen that lets users access Web applications, similar to what’s available on Mac or Windows machines. Meanwhile, in the next several weeks, Google’s document service will be available for editing even when users aren’t connected to the Internet.

Other improvements include built-in features for viewing Microsoft Office software, such as Word and Excel files. Users will also be able to easily access remote Windows computers, Pichai said.

Chromebook Prices, Features, Details

The upgraded laptop, called “Series 5 550,” is supposed to run two-and-half times faster the original machines, and boasts higher-definition video. Google also added features that will enable users to edit documents offline, read more content created in widely used Microsoft applications such as Word and Excel, and retrieve material from another computer at home or office. More emphasis is being placed on Chrome’s Web store, which features more than 50,000 applications.

The price: $449 for models that only connect to the Internet through Wi-Fi and $549 for a machine that connects on a 3G network. Samsung’s original Chromebooks started out with prices ranging from $429 to $499. Like the original Chromebooks, the next-generation machines feature a 12.1-inch screen display and run on an Intel processor.

Google and Samsung also are introducing a “Chromebox” that can be plugged into a display monitor to create the equivalent of desktop computer. The box will sell for $329.

The latest Chromebook and new Chromebox will be available online only, beginning in the U.S. Tuesday followed by a Wednesday release in the United Kingdom. The products will go on sale in brick-and-mortar stores for the first time in still-to-be-determined Best Buy locations next month.

The expansion beyond Internet-only sales signals Google’s determination to attract a mass audience to its Chromebooks, just as it’s done with smartphones running on its Android software. More than 300 million mobile devices have been activated on Android since the software’s 2008 release.

Without providing specifics, Pichai said several other computer manufacturers will release Chromebooks later this year. Google plans to back the expanded line of Chromebooks with a marketing blitz during the holiday shopping season in November and December.

One reason Google is confident Chromebooks will eventually catch on is because the Chrome Web browser has attracted so many fans in less than four years on the market. The company says more than 200 million people worldwide currently are using the Chrome browser.

Like other laptop and desktop computers, the Chromebooks will have to contend with the accelerating shift to the iPad and other tablets. The iPad 2, an older version of Apple’s tablet line, sells for as little as $399, undercutting the new Chromebook. Other low-cost tablets are expected to hit the market later this year. One of them might even be made by Motorola Mobility, a device maker that Google bought for $12.5 billion earlier this month. Google so far hasn’t commented on Motorola’s future plans for the tablet market.

The new Chromebooks also are hitting the market at a time when some prospective computer buyers may be delaying purchases until they can check out machines running on Windows 8, a makeover of Microsoft’s operating system that is expected to be released in September or October. Microsoft designed Windows 8 so it can be controlled through touch as well as keyboards. That versatility is expected to inspire the creation of hybrid machines that are part laptop, part tablet.

For more about Chrome devices, read here.

(Bloomberg and The AP contributed to this report.)