Philadelphia Mayor Michael Nutter and 17 other mayors are urging Congress to restrict the use of food stamps to buy soda and other sugary drinks.

The city leaders sent the letter as Congress is weighing cuts to the Supplemental Nutrition Assistance Program, the formal name for food stamps.

"It is time to test and evaluate approaches limiting SNAP's subsidization of products, such as sugar-sweetened beverages, that are contributing to obesity," the letter says.

The letter says the mayors "believe the program can do more to address the pressing challenge of obesity and diet-related disease," citing the more-than-one-third of American adults who are obese.

Nutter has twice tried and failed to enact a tax on sugar-sweetened beverages in Philadelphia, and has been outspoken about the issue.

In Philadelphia, nearly 68 percent of adults and 41 percent of youth between ages 6 and 17 are overweight or obese, according to the Centers for Disease Control and Prevention.

The American Beverage Association -- which represents the non-alcoholic beverage industry -- told the Associated Press that soft drinks shouldn't be singled out as a cause of obesity.

"Targeting struggling families who rely on (food stamps') vital safety net will not make America healthier or reduce government spending," the association said in a statement.

The office of New York City Mayor Michael Bloomberg released the mayors' letter. Bloomberg has received national attention for trying to ban sales of large-size sugary drinks and has previously tried to prevent food stamps from being used for soda.

The letter also expresses concerns about proposed cuts to the food stamp program and asks congressional leaders to maintain funding.