Japan's top diplomat on Tuesday reiterated Tokyo's concern over a strike on Iran's nuclear programme in an interview published as he began a two-day trip to Israel and the Palestinian territories.

"Japan is very concerned over the Iranian nuclear issue," Foreign Minister Koichiro Gemba told the top-selling Yediot Aharonot daily, in remarks translated into Hebrew.

"The international community, including Japan, is putting unprecedented pressure on Iran, and the renewal of talks between the world powers and Iran is a result of this pressure," he said.

Six world powers, known as the P5+1 grouping of diplomats from the United States, Russia, China, Britain, France and Germany, held a first round of talks with Iran over its contested nuclear programme in Istanbul last month, with a second round due to take place in Baghdad on May 23.

Israel says a nuclear Iran would constitute an existential threat to the Jewish state and has not ruled out a pre-emptive strike on Tehran's nuclear facilities.

"The military option will not only give Iran an excuse to expedite its nuclear programme, but could also increase the instability in the region, which would threaten Israel," Gemba warned.

The minister's remarks reiterated concerns that both he and Japan's Prime Minister Yoshihiko Noda had raised in mid-February during a visit to Tokyo by Israeli Defence Minister Ehud Barak.

At the time, Noda warned that military action could be "extremely dangerous" as it risks "escalating" the current situation.

And Gemba raised similar concerns, saying: "Using a military option would not only provide an excuse to Iran but could unite the Arab world against Israel."

On Monday evening, Barak said he had little confidence that the P5+1 talks would succeed in resolving the standoff over Tehran's nuclear programme.

"The P5+1 engagement with Iran, however, does not fill me with confidence. I may sound pessimistic but the state of Israel cannot afford to be duped," he told reporters at a Foreign Press Association meeting in Jerusalem.

He said that "all options to prevent Iran from getting nuclear weapons" were on the table, although he admitted that the military option would be "complicated."

"But a nuclear Islamic Republic of Iran would be far more dangerous," he said.

Gemba was due to arrive in Israel around midday for a two-day visit, which will see him meeting his Israeli counterpart, Avigdor Lieberman in Jerusalem.

On Wednesday he was to meet senior Palestinian officials in the West Bank city of Ramallah.

The UN Security Council has slapped four rounds of sanctions on Tehran over suspicions harboured by Israel and much of the West that Iran is seeking a militarised nuclear capability -- a charge which Tehran denies.