Comcast Corp, the largest U.S. cable operator, said on Monday it is introducing a wireless service for subscribers to access the Web beyond their homes anywhere within the United States.

The so-called fourth-generation (4G) wireless service, is the first execution of a partnership between Comcast, Clearwire Corp and other companies that use the emerging WiMax high-speed mobile technology.

Many consumers already update their blogs and watch videos using their mobile phones. Cable companies such as Comcast and Time Warner Cable Inc do not want to become irrelevant by restricting subscriber access to the home.

The new service, called Comcast High-Speed 2go, is expected to deliver data to laptops, netbooks and other devices over a wireless network at faster speeds than has been commonly available to date.

Comcast said it will offer download speeds of up to 4 megabits per second. Existing 3G wireless networks typically offer download speeds between 1 and 1.5 megabits a second.

Cablevision Systems Corp offers mobile Internet service via Wi-Fi, a short range service typically limited to a home, restaurant or hotspot. The operator is providing Wi-Fi service to its digital subscribers throughout its market in the New York metropolitan area.

Comcast High-Speed 2go launches officially in Portland, Oregon on Tuesday and is expected to expand to Atlanta, Chicago and Philadelphia before the end of the year, Comcast said.

A Metro version of the data card, which is typically installed into a laptop to allow wireless Internet access, will cost $49.99 a month when bundled with home Internet service. The Metro version will only work within the 4G metropolitan coverage area.

A nationwide version for $69.99 a month will allow subscribers to access the Internet via Sprint Nextel Corp's 3G network where the 4G network is not available.

WiMax is expected to blanket entire cities with Web access for mobile devices at speeds up to five times faster than traditional wireless networks, but the technology is still unproven.

After previous stumbles, such as a collapsed partnership with Sprint, cable companies are hoping that Clearwire, founded by wireless pioneer Craig McCaw will help them resolve their long-running wireless conundrum.

The cable industry is also trying to figure out ways to make more video available beyond traditional TV sets.

Last week Comcast and Time Warner Inc said they start testing ways to allow people to watch more TV shows over the Web, while making sure they keep paying for their traditional cable or satellite TV services.

Comcast will likely try to market the new wireless service as a way for subscribers to watch their favorite shows wherever they are in the United States.

(Reporting by Yinka Adegoke; Editing by Derek Caney)

Broadband Electronics Comcast