Bank of Japan Gov. Haruhiko Kuroda said Monday he will loosen the central bank's monetary grip "without hesitation" if conditions make that the sensible thing to do.

In a speech in Osaka, Kuroda expressed concern over falling prices as the central bank pursues its 2 percent inflation target.

He said that deepening the BOJ's negative interest rate and cutting the target for long-term interest rates, a policy adopted last week, will help make market conditions more accommodative.

"There can be cases where such powerful monetary easing is needed, depending on developments in economic activity and prices as well as financial market conditions," he said. "The bank stands ready to use every possible policy tool, if it judges that necessary, to achieve its objectives."

On Wednesday, the BOJ said it will modify the framework of its debt-buying program to keep the yield of the bellwether 10-year Japanese government bond around zero percent, while leaving its negative policy rate unchanged at minus 0.1 percent.

Kuroda promised to stoke 2 percent inflation as soon he took office early in March 2013, but he has failed to create even moderate levels of inflation in what has become a solo attempt to kick-start the economy following the government's abject failure to come through with much-promised structural reforms.

Consumer prices have been declining, due largely to the plunge in crude oil prices and tepid domestic demand following a consumption tax hike in 2014.

Kuroda has acknowledged it is taking more time than expected for to beat deflation and suggested that the BOJ may need to do more to push up prices.

The BOJ Policy Board also agreed last week to continue expanding Japan's monetary base until inflation reaches a steady 2 percent, retaining its target of ¥80 trillion of JGB purchases per year.