American Express Co. plans to announce today what is believed to be the first program designed to allow consumers to put their monthly mortgage payments on plastic -- and to earn credit-card rewards for doing so.

Mortgage bills, often the single largest payment people make every month, have been off limits to cardholders to collect points, largely because home lenders find it costly to pay card companies for processing the transactions. American Home Mortgage Investment Corp. and IndyMac Bancorp Inc., both among the nation's top 10 residential-mortgage originators, are the first two lenders to sign up for the program, with the idea of appealing to American Express's affluent clientele.

For American Express, the move represents its continuing efforts to drive credit-card acceptance in areas where cash or checks remain the dominant form of payment. The New York financial-services and travel company has teamed with various developers and property-management companies to enable customers to make down payments for luxury condominiums or pay rent on their American Express cards.

The mortgage-payment program is "just another progression for us in the real-estate area and in the luxury space," said Bill Glenn, who oversees American Express's relationships with its merchant customers in the U.S. and its global merchant network group.

To enroll in the program, American Express said its cardholders will have to pay a one-time fee of $395 to the mortgage lender to cover services such as account management and various perks. Once enrolled, cardholders will earn cash back, airline or hotel points, or other types of rewards their American Express cards offer.