US sues American Express

The Justice Department sued American Express yesterday, saying its rules preventing retailers from encouraging consumers to use cheaper, rival credit cards violate antitrust law. The Justice Department settled with Visa and MasterCard, which agreed to allow merchants to offer discounts to consumers who use less expensive types of credit or debit cards. The lawsuit has the potential to cut into a significant source of profits at American Express. The US credit card business vowed to fight the suit.