NEW YORK (AP) -- Worries of credit deterioration spreading from subprime mortgages into other sectors helped drag down bank stocks Tuesday.

After the market closed Monday, American Express Co. beat earnings estimates, but also said credit performance was declining. American Express customers typically have strong credit, another indication subprime problems could be spreading to the broader market.

Subprime mortgages are loans given to customers with poor credit history.

"As more companies are reporting, maybe it's becoming clear there is a broad-based credit problem," said Frank Braden, an analyst in Standard & Poor's equity research division.

National banks are making up for struggling general banking operations with growing profits in other divisions such as investment banking, Braden said. Despite the improved