WASHINGTON (AP) _ Frustrated dairy farmers are talking about dumping milk in their fields and pig pens if Congress refuses to prop up the lowest milk prices in a decade.

Farmers are angry and bitter that Congress left town for its August recess without passing a dairy relief bill that would have boosted milk support prices by 25 percent.

They're also fuming at the Bush administration's opposition to the legislation as they wrestle with milk prices that are below the costs of production.

A strike organizer, dairy farmer Bruce Krug of Constableville, N.Y., said dumping milk may be the only way to call attention to the plight of dairy farmers, who are expected to lose $3 billion this year under the lowest prices since 1978.

While milk prices at the farm have fallen 25 percent, the retail price drop has been smaller, according to Peter Vitaliano, director of policy analysis at the National Milk Producers Federation.

The price of a half-gallon of whole milk fell from $1.40 in June 1990 to $1.37 in June 1991, while the all-milk price at the farm fell from $13.95 per hundred pounds in June 1990 to $11.57 in June 1991, he said.

''Campaigns - whether economic or membership or presidential - are won and lost in television and the print media,'' said Larry Mitchell, director of state-federal relations for the American Agriculture Movement.

''And for farmers to win, they will have to couch it correctly, and show that what they're doing is not negative,'' Mitchell said.

Krug said the decision to dump milk wasn't made lightly and came after months of meetings and lobbying Congress.

''This strike is not something any of us are enjoying putting together,'' he said.

Krug said farmers in New York, Vermont, Pennsylvania and Missouri are organizing an Oct. 1 strike, and that farmers in other dairy producing states are also being contacted.

Mitchell said about 10 states will hold demonstration milk dumps Friday to draw support for the Oct. 1 strike.

Krug said striking farmers want to stop sending their milk to the dairy processors, who prepare it for retail sale.

''Probably the most common way is to pour the milk onto the ground of our fields to dispose of it,'' Krug said. ''Some farmers are talking about giving it to food banks. I'm going to offer mine to the people in the village.

''We just want to stop it from getting to the processors,'' he said. ''We are not directing this as the consumer.''

But Arden Tewksbury, a dairy farmer in Meshoppen, Pa., said he's afraid a strike could turn consumers against producers. And a congressional aide, who refused to speak on the record, agreed. He called the strike counterproductive when there's already a surplus of milk.

''It's hard to dance when you've shot off every toe you've got,'' the aide said.

Despite his reservations about the strike, Tewksbury said, ''I'm not willing to sit back and take this without fighting back.''

Tewksbury recently formed the Progressive Agriculture Organization, a group of Pennsylvania and New York farmers who got together to fight for higher dairy prices. He said he'll give Congress until mid- to late September to address the issue before deciding his next move.

Other producers are pushing their representatives and senators in a grass- roots campaign organized by the National Milk Producers Federation to get dairy relief legislation to a vote as soon as Congress returns in September.

''Effective grass-roots action provides the best, perhaps only, hope for a dairy bill to be enacted into law this year. Its success requires quick action by both cooperatives and their dairy farmer members,'' the federation's chief executive officer, James C. Barr, wrote members earlier this month.

''We want dairy legislation voted on before Congress adjourns this year,'' said Karl Hoyle, a federation consultant. ''If it's a crisis this year, it's a disaster next year.''

The federation, which represents about three-fourths of the nation's milk producers, estimates the legislation would boost cash receipts for dairy farmers by $15 billion over the next four years.

The Bush administration opposes the legislation, saying it would raise prices for consumers by about 10 percent a year between 1992 and 1995 and would increase the costs of federally funded food assistance programs such as school lunches.

Agriculture Secretary Edward Madigan also has said the bill would severely disrupt livestock markets, as farmers pare their herds to meet the production limits. He has said milk market conditions have begun to improve and market prices have begun to rise.