E-commerce giant Amazon.com Inc (AMZN.O) is fielding bids to replace U.S. lender JPMorgan Chase & Co (JPM.N) as the issuer on its co-branded credit card portfolio, a person familiar with the matter told Reuters. Amazon has sent out a "request for proposal" for the portfolio, the person said, asking not to be identified as the matter was not public yet. JPMorgan could fetch a 15% premium if it is replaced as partner in the portfolio, which contains more than $15 billion in credit card lending, Bloomberg reported earlier on Tuesday. American Express Co (AXP.N) and Synchrony Financial (SYF.N) were among those bidding on the portfolio, the Bloomberg report added. The financial firms didn"t immediately respond to requests for comment. Amazon and JPMorgan first issued a joint card in 2002 and their offerings have long operated on the Visa Inc (V.N) network. JPMorgan declined to comment when contacted by Reuters. Bloomberg said the lender was willing to part with the Amazon portfolio. Our Standards: The Thomson Reuters Trust Principles.