TOKYO Japan's top currency diplomat Masato Kanda warned against the yen's ongoing weakness on Wednesday, saying the authorities would take an appropriate response if moves become excessive.

"We are closely watching currency moves with a strong sense of urgency," Kanda told reporters. "We will respond appropriately if it becomes excessive."

He stopped short of strengthening the warning from a similar one issued by the finance minister on Tuesday, in a sign there may still be some time before any intervention to stem the yen's weakening.

Kanda was speaking to reporters after the yen slumped to a fresh seven-month trough versus the dollar overnight.

The Japanese currency fell 0.36% versus the greenback to as low as 144.02, its weakest since Nov. 10, as investors eyed a possible intervention by Japanese authorities.

Japan last conducted its rare yen-buying, dollar-selling intervention in September and October. Investors are eyeing a 145-yen threshold for intervention, a level around which the government stepped into the market in September.

(Reporting by Tetsushi Kajimoto and Takaya Yamaguchi; Editing by Jacqueline Wong and Jamie Freed)