ASHINGTON, March 18 — The Food and Drug Administration and the Environmental Protection Agency will recommend Friday that pregnant women, nursing mothers and young children eat no more than six ounces of albacore tuna or about one meal's worth each week, administration officials said.

Albacore tuna, often sold as canned white tuna, accounts for more than 5 percent of all seafood consumed in the United States, according to the FDA Recent tests have shown that albacore tuna has higher levels of mercury than other kinds of tuna. Mercury is known to affect neurological development of fetuses and young children.

The new guidelines will say that young children and women who are pregnant, nursing or planning to become pregnant can eat up to 12 ounces per week of light tuna, which has less mercury and accounts for about 13 percent of the nation's seafood consumption.

The agencies will continue recommending that those groups limit their intake of shark, swordfish, king mackerel and tilefish, which can also have high levels of mercury.

Fish that are low in mercury and safe to eat two or three times a week are shrimp, salmon, pollock and catfish, the advisory says.

An earlier draft of the advisory released in December made no specific recommendations about canned albacore tuna. That version noted only that canned albacore tuna generally contained higher levels of mercury than canned light tuna but said "you can safely include tuna as part of your weekly fish consumption." The draft was criticized by a federal advisory committee of physicians and scientists, which recommended that the agencies distinguish between albacore and other tuna.

"The advisory is clearly a step forward," said Michael Bender, the director of the Mercury Policy Project, a consumer advocacy group.

Diana Zuckerman, president of the National Center for Policy Research for Women and Families, said, "The good news for consumers is that the safer tuna is the least expensive."

The advisory committee had also wanted the agencies to recommend fish known to have lower mercury levels.

John Connelly, president of the National Fisheries Institute, a fishing industry trade group, said he hoped the list of low-mercury fish would head off any consumer flight from fish, a known source of protein. Focus groups have shown that "the target audience of young women threatened to move away from fish broadly, not just targeted fish," Mr. Connelly said. "We think that is a transfer of solid demonstrated benefits for a reduction in perceived risks."