Costco (COST) reported a 4% increase in sales at its more established stores during the month of July, however, the improvement was softer than the 5.1% expected.

The same-store sales figure, which includes sales at stores open longer than a year, was impacted by negative foreign exchange rates, partially offset by changes in gasoline prices.

Shares of Costco, which competes with BJ’s Wholesale and Wal-Mart (WMT), fell more than 2% to $116.87 in recent trade.

Meanwhile, the members-only warehouse said total sales were up 7% in the four-week period to $7.87 billion from $7.36 billion a year ago and up 8% to $94.91 billion for the 48-week period.

For the full year ending later this month, analysts are looking for fiscal 2013 revenue of  $105.8 billion. 

Follow Jennifer Booton on Twitter at @Jbooton