Rupert Murdoch has agreed to buy Triangle Publications Inc. for $3 billion in one of the most expensive media deals ever and one that would add TV Guide, the nation's largest-selling weekly magazine, to his empire.

The purchase of the privately held company from Walter Annenberg includes two other publications: the Daily Racing Form and Seventeen magazine, Murdoch said Sunday."These publications are the most valuable and prized publishing properties in the world," Murdoch said in a statement announcing the purchase by his News Corp.

The purchase of TV Guide raises anti-trust questions because of Murdoch's ownership of the Fox Television Network, said Andrew J. Schwartzman, executive director of the Media Access Project, a Washington, D.C.-based public interest telecommunications firm.

But a spokesman for Murdoch said TV Guide would be run separately from Murdoch's other holdings, which include newspapers and magazines on four continents.

Murdoch began negotiating with the 80-year-old Annenberg for Triangle a month ago.

"They (the Triangle publications) have been developed brilliantly by Ambassador Annenberg and we plan to make them the cornerstone of a great American publishing company," Murdoch said.

Annenberg, chairman of Triangle, said in a statement: "I am very happy that my publications are passing to Mr. Murdoch's company. I now plan to devote the rest of my life to education and philanthropy."

His past philanthropies include the establishment of the Annenberg School of Communications at the University of Pennsylvania, to which he has given one-third of Triangle's stock over the years.

The largest media takeover was Capital Cities Inc.'s $3.5 billion purchase of ABC in 1986.

Annenberg, who was U.S. ambassador to the Court of St. James in London during the Nixon administration, took over Triangle from his father in the 1930s. He founded TV Guide in 1952 and it quickly became Triangle's flagship, earning an estimated $75 million per year.

TV Guide has an audited circulation of more than 17 million copies.

Triangle was valued at about $1 billion last year by Wall Street analysts.