The Bank of Japan should use a combination of a more-negative benchmark rate and enlarged asset purchases ¡°sometime, before long¡± to help the economy, according to Etsuro Honda, an adviser to Prime Minister Shinzo Abe.

¡°But maybe not next week,¡± when the BOJ next meets to decide policy, Honda, 61, said in a phone interview Thursday. ¡°The BOJ is carefully watching the reaction from market participants¡± from its announcement of negative rates in January, ¡°so another round of monetary policy expansion will take place a bit after that.¡±

The unexpected move to charge commercial banks for a portion of the cash they park at the central bank roiled financial markets and continues to reverberate through the money-market industry. While lower rates would typically cause a cheaper currency, instead the yen has climbed ¡ª by 4.5 percent against the dollar, contributing to a drop in Japanese stocks. The shift has made it cheaper for Japan to borrow, with 10-year government bond yields now negative at auction out to 10-year maturities.

The market volatility comes as revised data this week confirmed the world¡¯s third-largest economy contracted in the final quarter of 2015, underscoring growing concern that Abe¡¯s reflation program is falling short of expectations. Consumer spending is dragging down growth, declining 0.9 percent in the October-to-December quarter from the previous three months.

Honda, who called for the BOJ to add stimulus before its January meeting, hinted at the possibility of a freeze on the current sales-tax rate of 8 percent, after last month saying the planned increase to 10 percent in April 2017 should be pushed back until 2019. The last hike in 2014 tipped the economy into a recession, and BOJ Governor Haruhiko Kuroda told parliament Thursday that its impact was larger and lingered longer than expected.

¡°I¡¯m so worried about the possible negatives of the next round of the consumption-tax hike,¡± Honda said. ¡°I recommend that we should postpone or freeze the implementation of the tax hike.¡±

Some Bank of Japan officials are increasingly seeing a potential delay to the 2017 consumption tax increase as a good thing for reaching the central bank¡¯s inflation target of 2 percent, according to people familiar with the discussions. This adds to signs the tide is turning toward a second delay to the tax hike ¡ª Abe previously delayed it from the original October 2015 timeline.

Honda, who also last month called for a stimulus package of about ?5 trillion, said a supplementary budget is needed to tackle the nation¡¯s stagnant consumption after discussions on the 2016 fiscal-year budget conclude this month.

He said the package should include infrastructure construction, assistance for child care and education, subsidies for science and technology development and payments to lower-income households.