Seeking to boost its sagging ratings, NBC is increasing its spending on advertising by 30 percent this television season, according to executives at the General Electric Co.-owned network.

NBC, which fell to fourth place last season after three years as the most-watched TV network, is focusing its advertising budget on three buzzed-about programs in the fall season: the redneck comedy “My Name is Earl,” Pentagon drama “E-Ring” and science-fiction thriller “Surface.”

NBC’s chief marketing officer, John Miller, told Bloomberg News that the promotional blitz acknowledges NBC’s slippage from the top of the broadcast heap. Miller declined to disclose the network’s advertising budget.

NBC lost about 16 percent of its young audience during the 2004-05 season and has been struggling to launch a breakout hit this season. Its advance bookings of commercials fell about 30 percent to $2 billion this season.