BENTONVILLE, Ark. — Wal-Mart Stores Inc. is throwing its weight behind organic products, a move that experts say could have the same lasting effect on environmental practices that Wal-Mart has had on prices by forcing suppliers and competitors to keep up.

Putting new items on the shelf this year — from organic cotton baby clothes to ocean fish caught in ways that don't harm the environment — is part of a broader green policy launched last year to meet consumer demand, cut costs for things like energy and packaging, and burnish a battered reputation.

Organic products are one lure for the more affluent shoppers whom Wal-Mart is trying to woo away from rivals such as Target Corp., said Alice Peterson, president of Chicago-based consultancy Syrus Global.

A new Supercenter in the Dallas suburb of Plano features more than 400 organic foods as part of an experiment to see what kinds of products can grab the interest of upscale shoppers.

"Like many big companies — they have figured out it is just good marketing and good reputation-building to be in favor of things that Americans are increasingly interested in," Peterson said.

Wal-Mart's Lee Scott is not the first chief executive to advocate sustainability — a term for the corporate ethos of doing business in a way that benefits the environment. General Electric Co., for example, last year began "Ecomagination," its program to bring such green technologies as wind power to market.

What makes Wal-Mart's efforts unique, sustainability experts say, is the retailer's power, from its sheer size, in relations with suppliers. Wal-Mart works closely with suppliers to shape goods that go into nearly 4,000 U.S. stores and more than 2,200 internationally.

Wal-Mart plans to double its organic grocery offerings in the next month and continue looking for more products to offer in areas such as grocery, apparel, paper and electronics.

Stephen Quinn, vice president of marketing, said Wal-Mart will have 400 organic food items in stores this summer "at the Wal-Mart price."

Some Wal-Mart critics call the effort just a public relations job. But others say Wal-Mart could make a real difference if it brings a critical mass of organic products to market and pushes more suppliers to adopt green practices.

Some of the new items will be seafood caught in the wild. Wal-Mart last month announced a plan to have all its wild-caught fish, which accounts for about a third of seafood sales, certified by the Marine Stewardship Council as caught in a sustainable way.

The London-based MSC, founded in 1997 as a venture of the conservation group World Wildlife Fund and global consumer products company Unilever, issues the certificates to let consumers know which fisheries avoid overfishing and use methods that don't damage the ocean environment.

Sustainability experts say what makes this program interesting is that Wal-Mart will work with its suppliers to get more fisheries around the globe certified by MSC, instead of just buying up the existing stock of certified fish.

Wal-Mart says this means there will be more sustainable fish that will also be available to its competitors, such as Whole Foods Market, which already sells about 18 MSC-certified items, according to the Web site for MSC. Wal-Mart plans to offer between 200 and 250 items.