By Tetsushi Kajimoto

TOKYO (Reuters) -Japan's top currency diplomat Masato Kanda said on Wednesday authorities will take appropriate steps against excessive moves in the yen, without ruling out any options.

One-sided, big moves in the yen would be considered "excessive," said Kanda, who is Japan's vice finance minister for international affairs, adding that he would not comment on whether Tokyo intervened in the exchange-rate market overnight to prop up the yen.

"Our stance against excessive move is unchanged," Kanda told reporters. He declined to comment on whether the overnight yen moves were excessive.

Kanda added that authorities were looking at various factors, including implied volatility, in determining whether yen moves were excessive.

After sliding below the psychologically important 150 mark, the yen strengthened sharply against the dollar overnight on Tuesday, leading some market participants to believe Tokyo had intervened to support the currency. The dollar stood at 149.100 yen in Asia on Wednesday.

(Reporting by Tetsushi Kajimoto; Writing by Leika Kihara; Editing by Chang-Ran Kim and Muralikumar Anantharaman)