WASHINGTON - The federal government wants to target childhood obesity with new limits for calories, sugar, fat and sodium on snacks sold in the nation's schools.

The Smart Snacks in School standards, announced last week by the U.S. Department of Agriculture, expand school nutrition standards for the first time to snacks, whether sold in the cafeteria, a vending machine or elsewhere.

Besides setting limits on fats, sugars and calories, the new rules would also limit portion sizes for drinks and snacks. Birthday parties, bake sales and school fundraisers would be exempt from the rules, which are scheduled to go into effect next July.

Most Arizona school officials welcomed the change, saying the state adopted similar nutrition standards for all school foods - including snacks - in 2006.

"Our schools are already ahead of the game," said Mary Szafranski, deputy associate superintendent for health and nutrition services at the Arizona Department of Education, who said the department supports the new regulations "without a doubt."

But others worried that there will not be enough time to study the impact of the new rules on students' diets or to get the new food choices in place.

Diane Pratt-Heavner, spokeswoman for the School Nutrition Association, said she thinks schools will do their best to meet the standards but worries about the impact on participation in school meal programs.