TOKYO, June 26 Reuters Japanese authorities were seriously concerned and on high alert about the yen39;s rapid decline, said the country39;s top currency diplomat Masato Kanda, escalating warnings as the currency languished at its weakest level in almost 40 years.

It is generally accepted that the current weakness in the yen is not necessarily justified, therefore believed to be driven by speculators, Kanda, vice finance minister for international affairs, told reporters on Wednesday.

The weak yen has become a headache for Japanese policymakers by boosting the cost of imported raw materials, pushing up inflation and hurting consumption.

Kanda said the recent moves in the currency were rapid and definitely onesided, moving away from his recent stance of not commenting on the ongoing market situation.

We have been preparing to act against excessive volatility, Kanda said, signalling his readiness for another intervention to support the yen.

Despite Kanda39;s warnings, the yen continued its downturn, touching 160.50 per dollar, the weakest in about 38 years.

The market has widely seen 160 yen to the dollar as authorities39; line in the sand, even though Kanda and other government officials have repeatedly said they had no specific levels in mind on when to intervene.

Japan spent 9.8 trillion yen 61.6 billion intervening in the foreign exchange market in April and May, after the Japanese currency hit a 34year low of 160.245 per dollar on April 29.

But those steps…