After months of negotiation, Comcast Corp. said Thursday it plans to buy a majority stake in NBC Universal for $13.8 billion in a deal with significant implications for Los Angeles’ entertainment industry.

The deal, which would give the largest U.S. cable TV operator control of two TV networks, several cable channels and a major movie studio, involve Comcast buying 51 percent of NBC Universal from General Electric Co. which convinced French conglomerate Vivendi SA to sell its minority stake first. GE has controlled NBC since 1986.

NBC Universal operations, largely concentrated in the Universal City area, include the NBC broadcast network, Universal Pictures, the Spanish-language Telemundo network, about two dozen cable channels including USA, Bravo and The Weather Channel, several regional sports networks, and several theme parks.

The deal is likely to undergo intense regulatory scrutiny, with both consumers and rival cable and satellite TV providers worried about rising costs for NBC content. Comcast in its announcement said it would maintain free, over-the-air TV on NBC stations, improve public interest programming, and not let its business interests affect NBC News content.

Under the deal, GE would buy Vivendi SA’s 20 percent stake in NBC Universal for $5.8 billion. NBC Universal would be separated into a new joint venture. Comcast would acquire a 51 percent stake in the new company with $6.5 billion in cash and the addition of $7.25 billion worth of its own cable channels such as E! and Style, which are located in Los Angeles’ Miracle Mile.

GE would retain a 49 percent stake and have option of divesting the stake in stages over seven years.