WASHINGTON (Reuters) - Britain's Royal Bank of Scotland Group Plc settled charges it had manipulated the Libor interest rate benchmark, the top U.S. derivatives regulator said, paying fines totaling $612 million to three regulators in the UK and the United States.

The bank neither admitted nor denied its findings, the Commodity Futures Trading Commission (CFTC) said, but a unit in Japan agreed to plead guilty to a criminal charge of wire fraud.

The bank will pay $325 million to the CFTC, $150 million to the U.S. Department of Justice, and 87.5 million pounds ($137.10 million) to the Financial Services Authority.

(Reporting by Douwe Miedema and Aruna Viswanatha; Editing by Gerald E. McCormick)