The Bank of Japan has yet to decide when it will next raise interest rates, BOJ Policy Board member Tadao Noda said Thursday, declining to be drawn into speculating on whether the bank will increase borrowing costs next month.

"Right now we have absolutely no preconceptions about how monetary policy will be managed," Noda said Thursday in a speech to business executives in Nara. "Personally, I assess economic statistics right up until each policy meeting."

Economists and investors expect the central bank to raise its overnight lending rate from 0.5 percent, the lowest in the industrialized world, at its Aug. 22-23 meeting. The Policy Board will be able to examine the impact of the July 29 Upper House election, second-quarter gross domestic product and data on production, prices and consumer spending.