Falling stocks and a rising yen raises speculation among investors the central bank will avoid saying anything to add to an outlook for higher rates. It will encourage investors to buy bonds.
Many investors are reluctant to trade actively before the central bank starts its two-day meeting Wednesday.
Market expectations appear to be accelerating and unless the central bank takes action soon, it may lose the market's confidence.
The latest data show that the year-on-year change in the core national CPI has been at or above the zero for the past three months. This should be interpreted as a sign that Japan is emerging from deflation, and this is in line with the central bank's view.