According to Reuters, there is no consensus within the BoJ yet on the preferred move at the July 29-30 rate review, as much will depend on the ECB's policy decision on Thursday and the market response, say sources familiar with the BOJ's thinking.

With robust domestic demand making up for weak Japanese exports, many BoJ officials see no imminent need to ramp up monetary support, and prefer to save its limited ammunition for when the economy faces bigger problems, the sources say.

But some officials worry that by standing pat at a time the U.S. and European counterparts are seen cutting interest rates or signal doing so, the BoJ risks appearing less dovish and sparking a yen spike that would hurt Japan's exports, they say.