SAN FRANCISCO (CBS/AP) — American Express is ending next year a 16-year-old agreement with Costco Wholesale that calls for the exclusive use of its cards at the retailer’s stores in the Bay Area and across the country.

The charge card company says it hasn’t been able to agree with Costco on renewal terms that make economic sense for American Express. The deal lasts until March 31, 2016.

American Express said Thursday morning that it charges Costco a significantly lower rate than the overall average it imposes on other retailers as part of the agreement.

A company spokeswoman says a similar agreement involving Costco’s Canadian stores ended last year.

A Costco Wholesale Corp. representative did not immediately return a call from The Associated Press seeking comment.

Shares of American Express Co. were falling in Thursday morning trading.

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