U.S. schools with vending machines that sell candy and soda to students could soon find the government requiring healthier options to combat childhood obesity under a bill introduced on Thursday by two senators.

While school meals must comply with U.S. dietary guidelines, there are no such rules on snacks sold outside of school lunchrooms. Many are high in fat, sugar and calories.

Senators Tom Harkin and Lisa Murkowski said their bill would allow the U.S. Agriculture Department to establish "common-sense nutrition standards" for food and beverages sold in school vending machines, stores and similar outlets.

Harkin, an Iowa Democrat, chairs the Senate Agriculture Committee, which oversees school lunch and breakfast programs that cost an estimated $11 billion a year in federal money.

U.S. child nutrition programs such as school lunches and the Women, Infants and Children feeding program are due for renewal this year. An Agriculture Committee spokesman said one option would be to include the legislation introduced today as part of the broader reauthorization later in 2009.

"Poor diet and physical inactivity are contributing to growing rates of chronic disease in the United States," said Harkin, a Democrat. "We must take preventative action now."

An estimated 32 percent of U.S. children fit the government's definition of being overweight and 16 percent are considered obese, at risk for serious health problems. Murkowski, a Republican from Alaska, said the bill was a response to "the youth obesity epidemic."

Harkin and Murkowski have offered similar legislation in prior years. The measure could have a better chance of passing this year with U.S. President Barack Obama's administration recognizing obesity as a top U.S. health threat.

Consumer and health advocacy groups including the American Dietetic Association, American Heart Association and the Center for Science in the Public Interest support the legislation.

Reginald Felton of the National School Boards Association said states and local communities should determine what is sold beyond federal programs because a "one-size fits all policy" would not sufficiently address the needs on a smaller level.

He also noted that some schools rely on snack sales to help cover costs.

"It's intrusive for the federal government to establish requirements beyond the programs that they fund, particularly when states are addressing the issue," said Felton. "If local boards want to restrict they should."