The world's largest retailer, Wal-Mart Stores Inc, on Monday said August same-store sales may beat its forecast of three to five per cent thanks to the strong start of back-to-school sales.

The Arkansas-based company said sales through August 15 were at the high-end of its monthly forecast and said although last week's power cuts affected around 200 stores it does not expect the blackout to have a material impact on sales or profits.

It added its best-selling categories so far this month include apparel and swimwear.