By Tetsushi Kajimoto

TOKYO (Reuters) - Japan's top currency diplomat Masato Kanda said on Wednesday that Japanese authorities won't rule out any options on currencies if speculative moves persist, a comment apparently warning against a sell-off in the yen.

It was the strongest warning since mid-August, when the Japanese currency slid past the key threshold of 145 per dollar. Since then, the authorities have stopped firing warning shorts, keeping traders guessing on Japan's intervention strategy.

Kanda, vice minister of finance for international affairs, was speaking to reporters after the dollar broke above 147 yen to edge closer to 148 yen overnight, this year's strongest ever against the Japanese currency.

The dollar has gained momentum on the view the Federal Reserve may raise rates one more time to cope with persistently solid inflation, while the Bank of Japan is expected to continue powerful easing to stoke demand-pull inflation driven by strong wage growth. Such policy diversion is behind the yen's weakness.

"We won't rule out any options if speculative moves persist," Kanda told reporters. "Needless to say, it's important for currency moves to reflect fundamentals."

Japanese core consumer prices, running at above 3% for more than a year has shown little signs of sustainable inflation accompanied by solid wage gains.