TOKYO - Japan's top currency diplomat said on Friday authorities would take action as needed in the foreign exchange market, resuming his jawboning after the yen's spike overnight raised market speculation about currency intervention.

Masato Kanda, who is vice finance minister for international affairs, declined to comment on whether authorities had intervened in the currency market to prop up the yen, but told reporters recent yen moves were out of line with fundamentals.

Chief Cabinet Secretary Yoshimasa Hayashi also told reporters on Friday that authorities were ready to take all possible means on exchange rates, signaling readiness to step into the market to arrest excessive yen falls.

The remarks on the yen break the recent silence among Japanese officials, who have refrained from commenting on their readiness to intervene as analysts question the effectiveness of jawboning in stopping sharp yen declines.

"I've found recent big currency moves strange, from the perspective of whether they were in line with fundamentals, and it would be highly concerning if the excessive volatility, driven by speculation, pushes up import prices and negatively affect people's lives," Kanda said.

"Currency interventions should certainty be rare in a floating rate market, but we'll need to respond appropriately to excessive volatility or disorderly moves," he added.

Finance Minister Shunichi Suzuki also told a regular news conference on Friday that rapid, one-sided moves in the foreign exchange market were undesirable.

The yen surged nearly 3% on Thursday in its biggest daily rise since late 2022, shortly after U.S. consumer price figures revived market expectations the Federal Reserve will cut interest rates in September.

GUESSING GAME

Some local media attributed the yen's abrupt spike to a round of official buying to prop up a currency that has languished at 38-year lows. The dollar stood 158.79 yen in Asia on Friday, after falling to as low 157.40 yen overnight.

"Japan likely intervened as otherwise, the yen won't move that much so suddenly," Takahide Kiuchi, an economist at Nomura Research Institute, said of the yen's overnight jump.

"Japan's past interventions were made when the yen was plunging, some of which weren't necessarily effective. This time it worked because authorities took action just when the weak-yen trend was turning around," he said.

Meanwhile, the Nikkei newspaper reported that the Bank of Japan conducted rate checks with banks on the euro against the yen on Friday, citing several sources.

Finance minister Suzuki declined to comment on whether authorities made rate checks, which are seen by traders as a precursor to actual yen-buying intervention.

Japanese authorities have recently made it standard practice to not confirm whether they have intervened in the currency market or not.

Tokyo spent 9.8 trillion yen ($61 billion) intervening in the foreign exchange market at the end of April and early May, official data showed, after the Japanese currency hit a 34-year low of 160.245 per dollar on April 29.

Back then, authorities were suspected to have intervened in several stages to create a buffer to defend the 160 mark against the dollar.

If Tokyo were to have stepped in on Thursday, it would have been more aimed at accelerating the yen's rebound against the dollar that occurred shortly after the weaker-than-expected U.S. inflation data.

All the same, some currency analysts were unconvinced that Thursday's price action was caused by intervention.

"The yen's surge last night looks to have been caused by stops triggered by weaker-than-expected U.S. consumer price data," said Daisaku Ueno, chief FX strategist at Mitsubishi UFJ Morgan Stanley Securities.

"Yen short positioning had been very stretched, not just against the dollar but other currencies," Ueno said, although he wouldn't rule out the possibility of intervention.

(Reporting by Makiko Yamazaki, writing by Leika Kihara; additional reporting by Mariko Katsumura and Yoshifumi Takemoto; Editing by Sandra Maler and Sam Holmes)