Both sides say they have consumers' interests at heart and are trying to minimize confusion about the term "sugar."

The U.S. Food and Drug Administration, which decides what goes on food labels, has ruled against the corn groups. The agency said calling high-fructose corn syrup "sugar" would mislead people - and could harm them.

"FDA's approach is consistent with the common understanding of sugar and syrup as referenced in a dictionary," the agency said in a letter posted on its website late on Wednesday.

The United States is the biggest consumer and manufacturer of high-fructose corn syrup. The sweetener was added to beverages such as Coca-Cola in the 1980s, but in recent years food makers have been trying out a return to sugar after some studies linked corn syrup to obesity.

The Corn Refiners Association petitioned the Food and Drug Administration to allow high-fructose corn syrup (HFCS) to go by "corn sugar," saying the two were nutritionally and metabolically equivalent.

Sugar groups disagree, and have sued the corn refiners group, as well as producers like Archer Daniels Midland Co and Cargill, to stop an advertising campaign that equates syrup with sugar.

The FDA said people associate sugar with being solid, dry, and crystallized, while syrup is aqueous or liquid.

"The use of the term 'sugar' to describe HFCS, a product that is a syrup, would not accurately identify or describe the basic nature of the food or its characterizing properties," the FDA said in the letter to the Corn Refiners group.

Currently, "corn sugar" can sometimes refer to dextrose, a type of sugar that is derived from corn starch. Some people have to rely on this corn sugar because they cannot absorb or tolerate fructose. The FDA said labeling high-fructose corn syrup as a sugar could put these people at risk.

Dan Callister, an attorney for the Sugar Association, called the FDA's decision "a victory for American consumers." But the Corn Refiners Association said the FDA did not question that corn syrup is a form of sugar, or that consumers could be confused by the term high-fructose corn syrup.

"In light of the FDA's technical decision, it is important to note that the agency continues to consider HFCS as a form of added sugar," the group's president, Audrae Erickson, said in a statement.

(Reporting by Anna Yukhananov; Editing by David Gregorio)

• A Permanent Economic Emergency