American Express said Wednesday MasterCard will pay it as much as $1.8 billion to settle an antitrust lawsuit, as it warned credit losses may increase as business conditions deteriorate.

American Express had accused the Purchase, N.Y.-based credit and debit card processor of conspiring to stifle some banks from issuing its credit cards. Last year, the company reached a $2.7 billion settlement with Visa Inc. in a similar suit.