The U.S. Department of Agriculture is considering buying 400,000 tons of sugar—enough for 142 billion Hershey 's Kisses—to stave off a wave of defaults by sugar processors that borrowed $862 million under a government price-support program.

The action aims to prop up tumbling U.S. sugar prices, which have fallen 18% since the USDA made the nine-month operations-financing loans beginning in October. The purchases could leave the price-support program with an $80 million loss, its biggest in 13 years, said Barbara Fecso, an economist at the USDA, in an interview.

The move would benefit companies that turn sugar beets and sugar cane into granulated sweetener, a business plied by American Crystal Sugar Co., Amalgamated Sugar Co. and U.S. Sugar Corp. The USDA wouldn't say how many companies have received loans, or identify them. U.S. Sugar said it doesn't have any USDA loans outstanding. American Crystal and Amalgamated didn't respond to requests for comment.

Higher prices would hit food companies including candy giants Mars Inc., Hershey Co. and Nestlé SA, and could ultimately boost retail food prices, at a time when many consumers are financially stretched.

"Clearly, the USDA has made up its mind that Big Sugar is going to trump the American consumer," said Pierson Bob Clair, president and chief executive at Brown & Haley, a confectioner in Tacoma, Wash., that makes Roca butter-crunch candy.