Japan must take steps against 'excessive, one-sided' yen moves, official says

"As for excessive, one-sided currency moves, we will closely watch developments and must take steps as needed," Kihara told a television program, when asked about the yen's recent falls.

The yen has recently fallen to 24-year lows against the dollar, as investors focus on the widening divergence between the U.S. Federal Reserve's aggressive interest rate hikes and the Bank of Japan's (BOJ) pledge to maintain ultra-low rates.

"I won't comment on monetary and interest-rate policy, as they fall under the jurisdiction of the BOJ," Kihara said.

Kihara also said the government will consider "in the not so distant future" steps to further open Japan's borders to overseas visitors, such as by scrapping a cap on the daily number of entrants.

"A weak yen is most effective in attracting inbound tourism," Kihara said, adding that further steps must be taken to draw in more foreign tourists into the country.

Japan eased border controls from Sept. 7 by raising the ceiling for daily entrants to 50,000 and freeing entry for travelers on package tours without the need for guides. read more

Analysts say scrapping the ceiling and allowing more travelers would be crucial to attract foreign money into Japan and revive its fragile economy.

On how to finance an expected increase in Japan's defense spending, Kihara said he would not rule out issuing government debt.

"Our goal is to drastically strengthen Japan's defense by tapping various sources of revenue. We'll be flexible on the funding and won't rule out any options," he said.

In a policy roadmap released in June, the government said it wanted to drastically increase defense spending "within the next five years," highlighting Tokyo's interest in boosting defense at a time of tension with its powerful neighbor China.