The Bank of Japan's unprecedented monetary stimulus can drive inflation to its 2 percent target, Gov. Haruhiko Kuroda said as the bank left its policy unchanged and trimmed its price outlook.

A slowdown in Japan's economy is unlikely to continue this quarter while inflation could pick up "quite fast" from the autumn, Kuroda said after the bank kept a pledge to expand the monetary base at an ¥80 trillion annual pace.

The governor stuck to his view that inflation will reach its target by September next year and, while he ruled out any immediate expansion in easing, reiterated readiness to act if necessary. A majority of economists doubt prices will pick up as the central bank envisions, with a third of those in a Bloomberg survey this month seeing further action in October.