First lady Michelle Obama and Food Network chef Rachel Ray discuss lunches with students from the Eastside and Northside Elementary Schools in Clinton, Miss., on Feb. 27, 2013. (Rogelio V. Solis/AP)

First lady Michelle Obama is set to take an unusual, high-profile step Tuesday into the center of a legislative battle by delivering White House remarks taking issue with makers of frozen pizzas and french fries and other companies seeking to scale back school lunch standards.

Obama is scheduled to speak out against a House measure, backed by Republicans and pushed by the food industry and some school officials, that would allow some districts to opt out of federal mandates passed in 2010 to reduce sodium and increase whole grains, fresh fruits and vegetables in school lunches. White House aides say she will announce the launch of a campaign-style push to fight the legislation.

The effort fits with the spirit of Obama’s “Let’s Move” campaign and other initiatives in which she has advocated for healthy eating and a reduction of obesity. Until now, however, she has largely shied away from direct confrontations with lawmakers and industry groups.

In addition to Tuesday’s event, White House officials will be speaking publicly this week and next about the benefits of the federal dietary standards, calling members of Congress to lobby for support and organizing scientific and advocacy groups to speak out.

The new dietary standards, authorized by the Healthy Hunger-Free Kids Act of 2010, already have produced what the White House says are noticeable improvements in children’s health.

The House Appropriations Committee is expected to approve language this week that would grant waivers from the new rules to school districts that report they are having problems complying.

“This is a serious threat to the tremendous progress we have made,” said Sam Kass, a White House assistant chef and nutrition policy adviser, noting recent data showing a decline in obesity rates among children. “This is a critical moment for our kids. We cannot afford to roll back effective programs. We need to be doubling and tripling our efforts.”

While the Obama administration and leading academic and school nutritionists are hailing the program’s success, others — including food-company executives and leaders of the School Nutrition Association — say the new rules have been costly and unwieldy and have led to a waste of food and money as students reject the imposition of healthier dietary rules.

This is not the first time food-industry officials have sought to weaken the White House-backed school lunch law. In 2011, frozen-food interests successfully pushed Congress to amend the rules so pizza with tomato sauce could be counted as a a vegetable and would meet the law’s new requirements for balanced nutrition in school cafeterias. Potato interests also have sought to change rules that restrict the sale of french fries and other potato products.

Lately, the School Nutrition Association, once an advocate for the new rules, has led criticism of the standards, saying that “plate waste” is piling up in school cafeterias and that local school nutritionists are having difficulty complying with the rules. The Agriculture Department has said that 90 percent of school districts are meeting the new standards — a statistic that the SNA disputes.

On Tuesday, the first lady is scheduled to join school nutritionists from around the country who say the program is working well. She will hear from an official from the Los Angeles Unified School District about the city’s success in putting in place higher dietary standards than those required by the 2010 federal law.

The first lady also will speak with New York City school officials and a nutritionist from a rural Georgia district who says the new lunch standards are popular and may have helped the school football team win a statewide competition. Also scheduled to make remarks is the past president of the School Nutrition Association, Helen Phillips, who has run school lunch programs in Norfolk, Va. Phillips worked with the White House to pass the 2010 legislation.

Her presence will highlight a dramatic change in the position of the SNA, which now backs Republican legislation to provide one-year waivers. The SNA receives funding from firms that supply foods to schools, such as Con-Agra, Domino’s Pizza and Schwan Food Co. Kass, the White House chef, and others say congressional Republicans are choosing to favor corporate preferences over the recommendations of nutritionists and physicians.

The current leadership of the SNA says it reached its positions after consulting with member school-district nutritionists.

“SNA’s request for flexibility does not come from industry or politics. It comes from thousands of school cafeteria professionals who have shown how these restrictive regulations are hindering their efforts to get students to eat healthy school meals,” said SNA President Leah Schmidt in an e-mailed statement.

Schmidt’s organization disputes administration claims that the program has been a success. “The administration’s own data shows that student participation is abruptly down in 48 states,” Schmidt said in her e-mail to The Post on Monday. “The White House needs to hear from the majority of school cafeteria professionals who are struggling to make these new standards work.”

Schmidt said her group supports the waiver as a temporary solution until Congress considers renewal of the school food law, which expires in 2015. White House officials and their allies see it as sinister. “It would gut the law,” says Margo Wootan, a nutrition expert with the Center for Science in the Public Interest.

The full House Appropriations Committee is scheduled to vote on the one-year waiver proposal on Thursday.

The first lady held a private call to rally supporters of the healthier food rules in advance of a House Appropriations subcommittee vote last week. Nonetheless, the waiver proposal passed easily on a voice vote.

“I want to do all I can to fight childhood obesity,” Rep. Rodney Davis (R-Ill.), who has been sharply critical of the standards, said in an interview before the vote. “But I’ve heard from school districts, superintendents, and they are asking for flexibility. This top-down approach from Washington isn’t working.”

A Democratic member of the committee, Rep. Rosa L. DeLauro of Connecticut, was the most outspoken opponent at the hearing and has said she will offer a number of amendments when the full committee takes up the measure.