America Online Inc announced Wednesday that it has signed an agreement with First USA Inc, the largest Visa and MasterCard lender in the US, that could be worth up to $500m for the online service. The five-year deal is being described by AOL as the internet’s largest advertising and marketing partnership to date and comes as an extension of an existing relationship between the two. AOL and First USA, a subsidiary of Chicago-based BankOne Corp, first offered a co-branded Visa card in 1996. With the new agreement, First USA becomes the exclusive marketer of credit card products and services on AOL, CompuServe, AOL.Com and AOL Instant Messenger in the US and Canada, and will also market products and services on AOL’s Digital City property. The deal is anticipated to generate up to $500m if certain undisclosed thresholds are met, most likely involving a specified number of accounts generated for First USA. But AOL said the agreement does contain a significant level of guaranteed revenue for it, as well as substantial marketing commitments to First USA. Through the partnership, First USA is looking to corner a large chunk of the US consumer internet audience, which it hopes will translate into millions of new customers. The credit card company has been active in its use of the internet to promote its services and last year signed a five-year $90m deal with Microsoft Corp to become the exclusive marketer of credit cards on the MSN.