TWO YEARS AFTER they forced MasterCard and Visa to scrap a joint debit card venture, a group of state attorneys general may be flexing their muscles for another antitrust attack on the bank-owned card associations.

This time, state officials are focusing on a linchpin of bank card economics - the interchange fees that are set by MasterCard and Visa to compensate card issuers each time a card is used at a retailing location. The suspicion is price-fixing.

Price-fixing allegations have been made before. As large-scale joint ventures of thousands of banks, both MasterCard and Visa have long been vulnerable to various types of antitrust accusations, but have successfully defended court challenges.