Bank of Japan Gov. Haruhiko Kuroda on Wednesday called a negative interest rate a "powerful weapon" for monetary easing, saying the bank will cut it again if needed to conquer deflation.
"The objective of monetary easing is to push down the entire yield curve," as lower interest rates would help companies and households, Kuroda said in a speech in Tokyo.
The BOJ surprised the market on Friday by announcing a rate of minus 0.1 percent on cash above a threshold that financial institutions hold at the central bank.