(Bloomberg News) JPMorgan Chase & Co. was ordered by arbitrators to pay $373 million to American Century Investments over claims that executives led by Jes Staley enriched the bank at the expense of the fund-management firm.

The award, issued privately in August, focused on JPMorgan's promise to promote American Century products when the bank acquired the firm's retirement-plan services unit, or RPS, in 2003.

Because Staley, then JPMorgan's asset-management chief, mistakenly thought there was a limit on the bank's liability if it didn't meet obligations, executives failed to make good on the deal, arbitrators found. Employees were instead rewarded for pushing JPMorgan's own products, according to the ruling.

"In short, JPM and RPS stacked the cards against ACI," the arbitrators wrote in the ruling.

The arbitrators awarded American Century $373 million plus 9 percent annual interest until paid in full.

JPMorgan, the largest U.S. bank by assets, set aside funds to cover the award during last year's third quarter. Parties in the case had agreed to resolve it privately through arbitration and the ruling had been sealed.

Staley, 56, was promoted to lead JPMorgan's investment bank in 2009.

The case was brought to the American Arbitration Association in 2009 and tried before a two-person panel in February and March of last year. In their ruling, the panelists said they reviewed about 600 exhibits and heard testimony from almost 50 witnesses, including Staley.

"Almost no one including the top executives of JPM and RPS down the chain of command paid any attention to what the revenue agreement said" unless it applied to the bank's own earnings, the arbitrators wrote.

"By actively planning the shift from ACI's funds" to those of JPMorgan to protect their own revenue, "JPM and RPS breached the revenue agreement," they said.

The ruling was reported earlier by Fortune magazine.

"We disagree strongly with the arbitrator's decision and award," Kristen Chambers, a spokeswoman for New York-based JPMorgan, said yesterday. "Among other things, it misinterprets the contract, ignores facts favorable to us such as the performance of certain American Century funds during the period in dispute, and ignores expert opinions that were favorable to us."

Chris Doyle, a spokesman for Kansas City, Missouri-based American Century, said the firm is "very pleased" with the decision.

"The panel found unanimously that JPMorgan actively breached its contractual obligations to American Century in order to enrich itself at our expense," he said.

The case is American Century Investment Management Inc. v. J.P. Morgan Invest Holdings LLC, 58 148 Y 00220 09, American Arbitration Association (Kansas City).