Japan's Finance Minister Taro Aso said on Thursday he had expressed deep concerns to U.S. Treasury Secretary Jack Lew over one-sided currency moves that earlier this week saw the yen hit its strongest levels in more than 17 months against the dollar. Aso met with Lew on the sidelines of a Group of 20 finance ministers' meeting in Washington that is expected to put currency policies high on the agenda. "I told (Lew) that excessive volatility and disorderly currency moves would have a negative impact on the economy. I also expressed deep concern over recent one-sided moves in the currency market," Aso told reporters. Arriving for the meeting, Bank of Japan Governor Haruhiko also described for the first time the yen's ascent so far this year as "excessive."

The exchange rate struck 107.63 yen per dollar on April 11, putting the Japanese currency at its strongest since October 2014. Aso said he also agreed with Lew, and gained understanding from G-20 counterparts, that a G-20 agreement to avoid competitive currency devaluations would not constrain monetary policy steps, including the adoption of negative interest rates, needed to achieve domestic economic objectives. The BOJ is struggling to achieve its 2 percent inflation target, which is a key part of premier Shinzo Abe's efforts to conclusively end a long phase of debilitating deflation. Asked whether the G20 accord meant Japan won't be constrained from intervening in the currency market to stem yen rises, Aso said: "The (exemption) applies broadly as there are various steps available on monetary policy and exchange rates."

A senior Finance Ministry official later clarified that currency intervention was not discussed at the meeting with Lew. The string of remarks underscore Japanese policymakers' strong concern over recent yen rises that could hurt already soft exports. Japanese officials' efforts to talk the yen down have failed to turn the tide as investors are betting that Tokyo won't be able to intervene due to a G-20 agreement in Shanghai in February warning against competitive currency devaluations. The U.S. Treasury Department issued a statement after Lew's bilateral meeting with Aso saying the two agreed on the importance of honoring G-20 currency commitments, suggesting that Washington is in no mood to allow Tokyo to intervene to weaken the yen. The onus may thus fall on the BOJ to use other policy tools to stop any spike in the yen, though its decision in January to deploy negative interest rates has failed to stem yen gains or boost stocks. Speaking in New York on Wednesday, Kuroda said the BOJ still had "many ways" to ease policy, including deepening negative rates or topping up asset purchases, suggesting that the central bank could expand stimulus at a policy review later this month.