Under a barrage of criticism that Wal-Mart Stores Inc. is bad for the overall economy, the world’s largest company is taking a public look at itself.

In an unusual move, Wal-Mart is sponsoring a gathering of noted economists who will debate the company’s effect on the economy and individual communities. The session, to be conducted Friday in Washington, is Wal-Mart’s latest step in a campaign to appear more open and repair its reputation among investors, politicians, employees and consumers.

Wal-Mart has built a $285 billion machine on a low-cost model whose prices have given it a competitive edge over its rivals.

Now, even as the discounter prepares for the holiday season with a public pledge to be even more aggressive on prices, it faces a dilemma on how to continue its momentum while also appeasing its critics. Negative publicity already has hurt its stock price and a tough economy has slowed its sales growth.