One of the U.S. central bank's most influential policymakers said on Thursday the bank is always scrutinizing banks and that it treats U.S. and European banks exactly the same.

William Dudley, the president of the Federal Reserve Bank of New York, was responding to a report in the Wall Street Journal that the bank is taking a closer look at the U.S. units of Europe's biggest banks, out of concern that a euro zone debt crisis could spill into the U.S. banking system.

We're always scrutinizing European banks, U.S. banks -- foreign banks, U.S. banks -- in terms of how they're doing, in terms of capital liquidity, credit quality, Dudley told the Newark Regional Business Partnership. So this is standard operating procedure, this is something that we do as a matter of course.

And it's really important to stress that we're not focusing on foreign banks any more than we're focusing on U.S. banks. We treat foreign banks and U.S. banks exactly the same, Dudley said.

(Reporting by Edith Honan, Editing by Chizu Nomiyama)