WASHINGTON A U.S. banking regulator said its supervisors could have been more aggressive in policing First Republic Bank's management of interest rate risk and uninsured deposits prior to its May failure, but it was unclear if that would have saved the bank in the face of the unexpected speed that depositors pulled their money.

The Federal Deposit Insurance Corporation said in a new report published Friday that a loss of market and depositor confidence ultimately sank the bank. However, it added bank supervisors were too "generous" in gauging some of its risks, and could have spent more time monitoring the rapidly growing firm in the years prior.

(Reporting by Pete Schroeder)