American Express is planning for a protracted legal battle with the Justice Department in order to defend its ability to structure merchant contracts as it sees fit, company officials said Wednesday.

Amex will ask a federal court to stay a recent ruling that its merchant contracts violated antitrust law, Chief Executive Kenneth Chenault said during the company's annual investor day in New York. U.S. District Court Judge Nicholas Garaufis ruled in February that the card company's rules prohibiting merchants from offering incentives to use specific card brands are illegal.

Garaufis had first ordered Amex and the department to seek a compromise on how to reform the practice, but he will now have to decide on a fix himself after the two sides found little common ground. Chenault said Amex will appeal once Garaufis issues his proposal and that he does not expect a quick resolution.

"We will ask for a stay so that our current merchant processes and customer experience stay in effect pending the outcome of the appeal," Chenault said. "Regardless of who won at this stage of the trial, it was highly likely that the outcome would be appealed and we were always expecting a lengthy process."

Amex, which charges merchants the highest average costs of any major card network, is concerned that it could lose market share if retailers are allowed to encourage the use of cheaper cards, a practice known as "steering." Amex is the only company still contesting the Justice Department's efforts over the past five years to stamp out the practice; Visa and MasterCard agreed to allow the practice in 2011.

Federal prosecutors want Amex's reforms to mirror the Visa and MasterCard settlements, an idea Chenault rejected. Amex wants to keep far more restrictive provisions about when merchants can offer perks.

"Fighting this suit was the right call in 2010 and continuing to fight is the right call now," Chenault said Wednesday. "Agreeing to the same settlement terms as Visa and MasterCard four and a half years ago would have been tantamount to a loss."

Some analysts wonder if that is true, and they question Amex's substantial financial investment in fighting the case. In practice retailers have shown little desire to use discounts or other perks to direct customers to cheaper payment methods even when they are permitted to do so.

Amex General Counsel Laureen Seeger argued Wednesday that the fight is about more than just finances — the company wants to defend its autonomy to structure merchant contracts as it wishes, she said.

"Whether or not steering is occurring today or will occur in the future, we wish to preserve our right to contract with our customers and our merchants the way that we feel is appropriate for the long term, and that's why we are maintaining the lawsuit," she said.

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