The U.S. Federal Reserve may have to raise interest rates from their currently ultra-low setting near zero percent before the need to take action is obvious, Fed Board Governor Kevin Warsh said on Thursday.

Warsh, in an op-ed published in the Wall Street Journal a day after the Fed left rates unchanged, also said the U.S. central bank was at a critical transition period, according to the Journal's sister organization, Dow Jones Newswires.

I would hazard the view that prudent risk management indicates that policy likely will need to begin normalization before it is obvious that it is necessary, possibly with greater force than is customary, Warsh said.

(Reporting by Alister Bull; Editing by Chizu Nomiyama)