The first lady accompanied Wal-Mart executives Thursday as they announced the effort in Washington. The company plans to reduce sodium and added sugars in some items, build stores in poor areas that don’t already have grocery stores, reduce prices on produce and develop a logo for healthier items.

"No family should have to choose between food that is healthier for them and food they can afford," said Bill Simon, president and CEO of Wal-Mart’s U.S. division.

As the largest grocer in the United States, Wal-Mart’s size gives it unique power to shape what people eat. The grocery business is nearly twice the size of No. 2 competitor Kroger. The company also has massive influence on products made by other manufacturers and sold at the store.

Mrs. Obama said the announcement has "the potential to transform the marketplace and help Americans put healthier foods on their tables every single day."

"We are really gaining some momentum on this issue, we’re beginning to see things move," she said.

The nation’s largest retailer plans to reduce sodium by a quarter and cut added sugars in some of its private label products by 2015. It also plans to remove remaining industrially produced trans fats. The foods Wal-Mart will concentrate on our products like lunch meats, fruit juices and salad dressings, items that contain high levels of sugar or sodium that consumers don’t know they’re ingesting..

A number of food makers have made similar moves, lowering sodium in their products based on shopper demand and increasing scrutiny by health groups. Bumble Bee Foods, General Mills Inc., Campbell Soup Co., PepsiCo Inc. and Kraft Foods Inc. all announced sodium reductions to their products last year.

During the press conference Wednesday, Andrea Thomas, Wal-Mart’s senior vice president of sustainability acknowledged those industry efforts but said,"Our goal is not to supplant these efforts, but to encourage their widespread adoption. We see our role as a convener and a catalyst. "

Food makers say they are trying to reduce sodium gradually, making it a more palatable change to its customers and giving the industry time to reformulate products. Most said they support efforts to curb sodium in American’s diets but are waiting to see if the Food and Drug Administration decides to mandate a reduction.

Wal-Mart said it would reduce prices on fruits and vegetables by $1 billion a year by attempting to cut unnecessary costs from the supply chain. The company also said it would work to reduce price premiums on healthier items made with more expensive ingredients.

"Our customers often ask us why whole wheat pasta sometimes costs more than regular pasta made by the same manufacturer," said Thomas.

Mrs. Obama has a history of working with Wal-Mart. She once served on the board of Westchester, Ill.-based TreeHouse Foods Inc., a food supplier for the store, but resigned in 2007 while her husband was campaigning for the presidency. Barack Obama had criticized the store over wages and benefits it pays employees.

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AP Retail Writer Anne D’Innocenzio in New York contributed to this report.