Wal-Mart Stores Inc is headed to Washington to unveil its plan to promote healthier and more affordable food options at its stores.

The world's largest retailer did not provide details of its initiative, which is set to be unveiled by some of the company's top executives on Thursday morning.

The move comes as U.S. first lady Michelle Obama leads an administration initiative to combat child obesity. She has pushed food makers to quickly reformulate food to make it healthier.

Wal-Mart has already discussed its goal to bring lower-priced, healthier foods to urban areas known as food deserts that do not have traditional grocery stores, as it tries to expand in urban areas like Chicago, New York and Washington D.C.

According to the New York Times, Wal-Mart plans to make thousands of its packaged foods lower in unhealthy salts, fats and sugars, and to drop prices on fruits and vegetables. The Times also said that Mrs. Obama will attend the announcement in Washington.

Wal-Mart is the largest seller of food in the United States, so any move it makes can have a ripple effect in the food supply chain. It also has the potential to impact everyone from farmers to grocery stores, drugstores and dollar stores, who have been beefing up their food offerings.

The battle for food spending is heating up, even before Wal-Mart's new initiative. Target Corp , Family Dollar , Walgreen Co and others have dedicated more space to food in their stores. They hope that by providing a wider variety of items people will come into their stores more often, and spend more when they visit.

Such shifts in the food industry have added pressure to grocery stores, which already face soaring costs.

Wal-Mart sells a wide variety of food from companies such as Kraft , Unilever and PepsiCo

and sells food under its Great Value private brand.

Changes that Wal-Mart spearheads spread much further than its store doors. A few years ago, detergent makers such as Procter & Gamble Co

quickly reformulated their products to remove water and reduce package sizes after Wal-Mart pushed suppliers for more environmentally-friendly products. The manufacturers absorbed millions of dollars in costs to meet the changes Wal-Mart was asking for.

(Reporting by Jessica Wohl, additional reporting by Sakthi Prasad in Bangalore, editing by Dave Zimmerman)

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