WASHINGTON — A prominent consumer advocacy group sued the U.S. Food and Drug Administration on Thursday for failing to regulate the amount of salt in the nation’s food supply. The Center for Science in the Public Interest wants the FDA to act on the group’s 10-year-old petition to lift salt’s status as “generally recognized as safe.” Doing so would reclassify salt as a food additive, which subjects it to more stringent regulation, like limits on the amounts allowed in processed foods. The legal action is the latest chapter in the group’s decadeslong efforts to combat excessive sodium consumption. “For more than 35 years, FDA has dragged its feet… ,” the group’s president, Michael F.