Itsunori Onodera gave the stark warning to his US and South Korean counterparts in talks earlier today.
Mr Onodera’s remarks underscored the deep concern in Tokyo after North Korean weapons tests, including test firing missiles over Japan, as Pyongyang seeks to develop a nuclear-tipped missile capable of reaching the mainland US.
His comments broke from more measured language earlier on Monday by US Defence Secretary James Mattis and South Korean Defence Minister Song Young-Moo, as the three men met on the sidelines of a gathering of Asian defence chiefs in the Philippines.
He said: ”The threat posed by North Korea has grown to the unprecedented, critical and imminent level.
“Therefore, we have to take calibrated and different responses to meet with that level of threat.”
South Korea’s Mr Song also acknowledged “North Korea’s provocative behaviour is becoming worse and worse,” in public remarks before reporters were escorted out of the meeting room.
General Mattis renewed sharp criticism of North Korea’s tests, saying they “threaten regional and global security”.
The US defence minister, who kicked off a week-long trip to the region on Monday, has been eager to emphasise diplomatic efforts to resolve the crisis peacefully as escalating tension between Washington and Pyongyang stoked fears of “armed confrontation”.
Asked about his conversation with Mr Onodera after the two met earlier in the day, before joining South Korea’s Mr Song, the American said they discussed “maintaining stability and peace in support of the diplomats”.
Former US president Jimmy Carter has again said he is willing to travel to North Korea on behalf of the Trump administration to help diffuse the situation.
General Mattis has been more cautious in his public remarks than US President Donald Trump, who has been locked in a war of words with North Korean leader Kim Jong-un, threatening to destroy the rogue state to defend the United States and its allies.
Kim has blasted Mr Trump as “mentally deranged”.
The American defence minister is at the start of a week-long trip to Asia and will attend meetings hosted by defence ministers from the Association of Southeast Asian Nations (ASEAN) in the Philippines.
ASEAN defence ministers, in a joint statement, expressed “grave concern” over North Korea’s nuclear and missile programmes and urged the reclusive country to meet its international obligations and resume communications.
They underscored the “need to maintain peace and stability in the region” and called “for the exercise of self-restraint and the resumption of dialogue to de-escalate tensions in the Korean peninsula”.
General Mattis’ trip, which will include a stop in Thailand, comes before Mr Trump’s first visit to Asia next month, including a stop in China.
The President has been pressuring China, North Korea’s neighbour and sole ally, to do more to rein in the hermit kingdom’s missile and nuclear programmes.