Banks have become so wary about lending that credit costs are being pushed up despite sharp cuts in official interest rates and that is adding to the risks of an economic downturn, the vice chairman of the Federal Reserve said Thursday.

Donald Kohn

"It is reducing the values of some assets and tightening credit cost and availability across a wide range of instruments and counterparties, despite considerable easing in the stance of monetary policy," Donald Kohn said in prepared remarks.