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A couple of high-profile senators are expressing misgivings about a deal for Comcast  to purchase a majority stake in NBC Universal, which would give the nation's largest cable TV operator control of an array of cable channels and a major movie studio.

The fears come as the two companies announced a $13.75 billion buyout that would give Comcast take a 51-percent share and let General Electric keep a 49-percent minority stake.

Sen. John D. Rockefeller, chairman of the U.S. Senate Committee on Commerce, Science and Transportation, needs regulatory oversight.

"When major media companies swell to control both content and distribution, we need to make sure consumers are not left with lesser content and higher rates," he said.

Sen. John Kerry, chairman of the Commerce Subcommittee on Communications, Technology and the Internet, said the deal is something that he wants Congress and the Obama administration to look into before it goes through.

"The Comcast-NBC deal announced is extremely significant in scope and raises some complex questions," Kerry, D-Mass. "My subcommittee will monitor that process closely to ensure that any legitimate anticompetitive and public interest concerns are fully addressed."

Comcast, which already serves a quarter of all U.S. households that pay for TV, would gain control of the NBC broadcast network, the Spanish-language Telemundo and about two dozen cable channels, including USA, Bravo and Syfy. It also would have regional sports networks, Universal Pictures and theme parks.

If the deal clears regulatory and other hurdles, Comcast would rival the heft of The Walt Disney Co., which Comcast CEO Brian Roberts already tried to buy.

Roberts said bringing NBC Universal into the Comcast family is "pro-consumer" and would allow the company to more quickly deliver "what consumers want, which is access to all different types of content on different platforms and different times."

Already Democratic lawmakers have expressed wariness over media conglomeration, and have suggested the government may even have a role to play in propping up failing newspapers. At the same time, they are looking at preventing media companies from owning both a newspaper and a television station in the same market.

Although the deal could mean that movies could reach cable more quickly after showing in theaters, and that TV shows could appear faster on cell phones and other devices, it also raised concerns that Comcast would wield too much power over entertainment.

Rep. Henry Waxman, chairman of the House Energy and Commerce Committee, said Thursday that he will closely monitor a would-be merger.

"The proposed Comcast-NBC Universal joint venture agreement has the potential to reshape the media marketplace. This proposal raises questions regarding diversity, competition and the future of the production and distribution of video content across broadcasting, cable, online and mobile platforms. It is imperative that the FCC, the Justice Department, and the FTC rigorously assess whether this transaction is in the public interest," Waxman said, vowing to hold hearings.

But Comcast counters that its own business is threatened by online video and more aggressive competition from satellite and phone companies that offer subscription TV services.

Still, consumer advocates and even other cable operators worry about the deal, saying people could end up paying more for TV, and the combination would be so threatening that rivals would strike similar deals just to compete.

If media ownership were further concentrated, consumers would see higher prices and fewer choices, said Andrew Jay Schwartzman, chief executive of the Media Access Project. He warned that online video and other new forms of competition could be squashed "before they can gain a toehold in the market."

Satellite TV rival Dish Networks Corp., meanwhile, worries that Comcast would be in a stronger position to withhold channels from competitors. CEO Charles Ergen has complained that a regulatory loophole lets Comcast bar his company from carrying Philadelphia sports games shown on Comcast's regional sports network. Comcast did not respond to requests for comment.

Any deal may come with some restrictions, such as treating rival cable, satellite TV and phone companies equally in programming talks instead of favoring its own cable operations. That is one of the big concerns among those who back net neutrality rules as a way to prevent service providers from blocking content to rival companies.

Comcast would buy its 51 percent stake of the new company by paying $6.5 billion in cash and contributing $7.25 billion worth of cable channels it owns, including E!, Style and Golf Channel.

But if the deal wins approval, Comcast would still have to make it work, and prove it can do a better job than Time Warner, which couldn't find a way to make its cable, AOL and content businesses operate well together.

The Associated Press contributed to this report.