SAN FRANCISCO (Reuters) - Google Inc is actively negotiating with three television networks that have blocked access to their websites on Google TV, a source familiar with the matter said.

Google Inc CEO Eric Schmidt introduces Google TV, blending web technology and television, in collaboration with various partners, at the company's annual developer conference in San Francisco, California May 20, 2010. REUTERS/Robert Galbraith

Three of the biggest U.S. television broadcasters have blocked the Web-based versions of their shows from Google’s new Web TV service, throwing a wrench into the company’s plans to expand from computers to the living room.

Representatives from Walt Disney Co and NBC Universal confirmed on Thursday that the companies blocked access to the broadcast TV shows available on their websites from Google TV. Disney owns ABC network and cable TV business ESPN.

News Corp’s Fox is also considering blocking access to shows on its website, but a decision has not yet been made, a source familiar with the matter said.

CBS has blocked access to full-length episodes of their programs, including popular shows like “CSI: Crime Scene Investigation,” according to a report in the Wall Street Journal on Thursday.

CBS declined to comment.

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Google TV, which became available this month in the United States, allows consumers to access Web content on their television screens.

The service is built into devices from Sony Corp and Logitech International and could open new advertising opportunities for Google, which generates the bulk of its roughly $24 billion in annual revenue from Web search ads.

But Google’s TV plans may be viewed as a threat by established television businesses, said Gartner analyst Van Baker.

“Everybody knows the lock that Google has on Internet traffic in terms of advertising. If you take that model and you extend it to television, suddenly Google’s power becomes enormous in the advertising space and the broadcasters don’t like that idea,” Baker said.

Google said in a statement that its new Google TV service “enables access to all the Web content you already get today on your phone and PC, but it is ultimately the content owner’s choice to restrict users from accessing their content on the platform.”

Earlier this month, Google announced that HBO would offer access to hundreds of hours of its programing to existing subscribers through Google TV, and said that Turner Broadcasting has optimized some of its most popular websites, including sites for TBS, TNT and CNN, for Google TV.