The television networks, typically among the most recession-resistant of all businesses, are beginning to feel the impact of a slowdown.

Confronted by hesitant advertisers, ABC, NBC and CBS, along with Fox Broadcasting Co., have entered into a discounting war designed to sell unsold commercial time.

The price fight has reversed the usual dynamics that govern the television marketplace: Advertisers who buy TV commercials now, in the so-called "scatter" market, are paying less than those who bought time for the fall season last spring during what is known as the "upfront" buying season. The current discounts range anywhere from 10 percent on the most popular prime-time programs to as much as 40 percent for shows that are ratings laggards.

"This is the softest the marketplace has been in 10 years," said Paul Schulman, whose New York firm negotiates network buys for such companies as Ralston Purina Co., MGM-UA Communications and Mobil Corp. In a typical year, Schulman said, scatter-market prices are 10 percent to 15 percent more expensive than upfront prices, particularly in the fourth quarter, when companies begin their holiday promotions on television.

On ABC's "Monday Night Football," for example, 30 seconds of commercial time sold for an average of $240,000 before the fall season began; now, a 30-second slot costs between $190,000 and $200,000, media buyers said.

Executives of all three networks confirmed the general trend but declined to be more specific about ad rates being charged.

The slowdown in advertising also has hit newspaper and magazine publishers. But some additional forces at work in the television industry have made the impact there particularly acute. Fox's expansion of its prime-time schedule from three nights a week to four this season has increased the supply of available time for network advertisers, as has an increase in the number of prime-time ads being sold by the networks.

Added to this is the increased competition for advertising dollars the networks face from cable television, syndicated programming and so-called unwired networks -- ad hoc groups of independent stations that air a special program on a given night.

Ad agency and network sources said the fall season also has been hurt by external economic factors such as skittishness over the federal budget stalemate and the Persian Gulf crisis and uncertainty about the economy.

"We're in a recession, whether people want to acknowledge it or not," said Bill Croasdale, who directs network TV buying for Backer Spielvogel Bates, the ad agency for Wendy's International, Campbell Soup Co., Avis Europe PLC and Mars Inc. "A lot of {advertisers} are waiting to see what their third-quarter sales are before they're going to release money for {TV ads}. If you have any doubts, you sit on your discretionary dollars as long as you can."

The tumbling prices for network commercial time have helped speed a similar slide at Washington-area TV stations, which must keep their rates competitive with their national brethren. Rick Gold, local sales manager at WTTG, Channel 5, the Fox station in Washington, said his station has seen its revenue fall by about 10 percent this year. Especially hard hit, he said, were the prime-time hours, which attract the biggest audiences and are the most expensive for advertisers.

Ironically, the disappointing ratings of many of the new fall programs may ultimately work in the networks' favor. Ratings that fall below levels guaranteed to advertisers force the networks to provide sponsors with free air time; the "make good" ads will soak up some of the unsold commercial time, thus raising prices for the remaining time, said Werner Michel, senior vice president of corporate programming for Bozell Inc., a New York ad agency.

"The best we can say is that it hasn't been a disaster," a network sales executive said. "There is no doom and gloom. It's been tough, but we'll survive."