Wal-Mart Stores Inc. is planning an aggressive push into urban markets with a new small format that's a fraction of the size of its supercenters.

The expansion is aimed at pumping up sluggish U.S. sales. The retailers is expected to spell out more details next month at a meeting with analysts.

Real estate executives say that this summer the world's largest retailer has been scouring for small locations, around 20,000 square feet, in urban areas including New York City and San Francisco. That's larger than a typical drugstore but smaller than a supermarket.

Wal-Mart just reported its fifth straight quarterly decline in revenue at U.S. Walmart stores open at least a year. That's considered a key indicator of a retailer's health.