WASHINGTON — Wal-Mart, the nation’s largest retailer, will announce a five-year plan on Thursday to make thousands of its packaged foods lower in unhealthy salts, fats and sugars, and to drop prices on fruits and vegetables.

The initiative came out of discussions the company has been having with Michelle Obama, the first lady, who will attend the announcement in Washington and has made healthy eating and reducing childhood obesity the centerpiece of her agenda. Aides say it is the first time Mrs. Obama has thrown her support behind the work of a single company.

The plan, similar to efforts by other companies and to public health initiatives by New York City, sets specific targets for lowering sodium, trans fats and added sugars in a broad array of foods — including rice, soups, canned beans, salad dressings and snacks like potato chips — packaged under the company’s house brand, Great Value.

In interviews previewing the announcement, Wal-Mart and White House officials said the company was also pledging to press its major food suppliers, like Kraft, to follow its example. Wal-Mart does not disclose how much of its sales come from its house brand. But Kraft says about 16 percent of its global sales are through Wal-Mart.