American Express recently reported quarterly earnings, showing that its single-biggest expense was credit card rewards.
The warehouse retailer will accept only Visa come June, then bump membership fees.
As profits plummet, the company faces intense competition for affluent customers.
The issuer of the famous Black Card is focusing on low-income financial services.
American Express will reveal a line of "League of Legends"-themed debit cards, in which cardholders can earn rewards points for in-game currency.