Restaurants could no longer use sulfites to preserve fresh potatoes under a ban proposed yesterday by the Food and Drug Administration.

Sulfites were banned last year as a preservative for raw fruits and vegetables. Restaurants and wholesalers frequently use sulfites to keep sliced or peeled potatoes from turning brown before they are cooked.

In proposing to expand that ban, the FDA said four deaths have been linked to exposure to sulfite preservatives used on raw potatoes that subsequently were served by restaurants as hash browns and cottage fries.

FDA Commissioner Frank E. Young said that the agency has concluded that sulfite preservatives pose no health hazard to the general public, but can cause reactions in up to 1 million people allergic to them, many of whom suffer from asthma. Reactions range from hives, itching, dizziness, nausea and diarrhea to shortness of breath and, in rare cases, fatal shock, the FDA said.

The new rule, to be published in the Federal Register today for a 60-day public comment period, would eliminate use of sulfites by restaurants on fresh potatoes to be served or sold unpackaged and unlabeled. It also would apply to wholesalers that supply restaurants and such institutions as nursing homes and hospitals.