WASHINGTON — Michelle Obama is urging the nation's largest food companies to speed up efforts to make healthier foods and reduce marketing of unhealthy foods to children.

Obama asked the companies, gathered at a meeting of the Grocery Manufacturers Association on Tuesday, to "step it up" and put less fat, salt and sugar in foods.

"We need you not to just tweak around the edges but entirely rethink the products you are offering, the information that you provide about these products, and how you market those products to our children," she said.

The first lady has talked to schools and nutrition groups across the country in her effort to reduce childhood obesity. This is the first time she has confronted the food companies that make the snacks and junk food that stuff grocery aisles and school vending machines.

The Grocery Manufacturers Association — which counts Kraft Foods Coca Cola and General Mills among its members — invited her to speak at its science forum this week and attendees gave her a standing ovation.

Welcoming the first lady and embracing her campaign for healthier children, launched earlier this year, could have advantages. The industry is positioned to take some blows in the coming year, including a child nutrition bill about to move through Congress that could eliminate junk food in schools, digging into some companies' profits.

The Food and Drug Administration is also beginning to crack down on misleading labeling on food packages, saying some items labeled "healthy" are not, and the Senate last year mulled a tax on soda and other sweetened drinks to help pay for overhauling health care.

That tax did not make it into the health care bill, but it could be seen as an opening shot in a quietly growing effort to target food companies, especially as local, state and federal governments scrounge for revenue in a tight fiscal environment.

Obama said she would like to see less confusing food labels and portion sizes and increased marketing for healthy foods. She urged companies not just to find creative ways to market products as healthy but actually increase nutrients and reduce bad ingredients.

Obama's campaign is largely focused on school lunches and vending machines, along with making healthy food more available and encouraging children to exercise more.

Scott Faber, a lobbyist for the grocery association, said the industry is open to working with the government on finding ways to produce healthier foods.

"Consumers are demanding more and more healthy choices," he said.

While introducing Michelle Obama Tuesday, Rick Wolford, chairman and CEO of Del Monte Foods and chairman of the Grocery Manufacturers Association, said it is "a watershed moment in the fight against obesity."