Costco Wholesale (COST) reported same-store sales increased 6% for the month of June, putting its shares on track to open near all-time highs on Thursday.

Shares of Costco were up 1.5% to $115.30 in pre-market trade, near their all-time high of $114.83 reached on May 28.

The Issaquah, Wash.-based warehouse retailer said total sales for the five weeks ended July 7 increased 8% to $9.92 billion from $9.16 billion a year ago.

Gasoline prices had a slightly positive impact on same-store sales, a key growth metric for retailers that measures sales at stores open longer than a year, while Costco said foreign exchange rates weighed negatively.

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