TOKYO (Reuters) - Japan's top currency diplomat Masato Kanda said on Wednesday he would have to respond if speculators cause excessive moves in the currency market and that there was no limit to how often authorities could intervene, Kyodo News reported.

"I have no choice but to respond appropriately if there are excessive moves caused by speculators," the vice finance minister for international affairs told Kyodo in an interview.

The dollar fell about 1.2% to 156.34 yen on Wednesday, with traders suspecting another round OF official buying from Tokyo, after Japanese authorities last week likely stepped in to haul the currency away from 38-year lows.

The Ministry of Finance was not immediately available for comment.

Bank of Japan data released a day earlier suggested Tokyo may have intervened to prop up the yen over two straight days last week - on Thursday and Friday - spending an estimated 6 trillion yen ($38.38 billion). The government has said it would not confirm whether authorities had intervened in the market.

Kyodo also quoted Kanda as saying that while there were various factors behind currency moves, "the biggest is speculation."

In comments that appeared to be a tacit confirmation of authorities' action, he added: "We are communicating very closely with the authorities of each country and complying with international agreements, so there has been no criticism from other countries."

($1 = 156.3300 yen)

(Reporting by Satoshi Sugiyama and Chang-Ran Kim; Editing by Kim Coghill)

By Satoshi Sugiyama