Japan may have to brace for a North Korean missile tipped with a hydrogen bomb flying over the archipelago if Pyongyang tests such a device in the Pacific Ocean, Defense Minister Itsunori Onodera said Friday.

“If the hydrogen bomb is going to be delivered by a ballistic missile, we cannot rule out the possibility that it will fly over Japan,” Onodera said, after North Korea indicated it may test a hydrogen bomb following President Donald Trump’s recent U.N. address, in which he warned the United States will have “no choice but to totally destroy North Korea” if it needs to defend itself or its allies.

North Korean leader Kim Jong Un said Washington could face the “highest level of hard-line countermeasure” in a statement carried by the official Korean Central News Agency on Friday. The country’s Foreign Minister Ri Yong Ho said the “highest level” action may be a hydrogen bomb test in the Pacific Ocean.

Chief Cabinet Secretary Yoshihide Suga said the Japanese government will remain highly vigilant so that it can “deal with any kind of situation.”

Onodera, speaking later in a lecture organized by the Asian Research Affairs Council in Tokyo, said the remarks by the North Korean foreign minister “cannot be downplayed.”

“What may come next is an intercontinental ballistic missile and a nuclear test that is not conducted underground. And if that takes place in the Pacific Ocean, the impact will be even more huge,” the minister said.

Onodera emphasized that “diplomatic efforts” are the most important in addressing the situation, while underlining the need to continue to add pressure on North Korea to prevent the country from engaging in further provocative actions.

“What the Defense Ministry and the Self-Defense Forces should do is to make the Japan-U.S. alliance firm and ensure that will be well recognized by North Korea,” he said.

Japan faces an increasing threat from North Korea’s nuclear and missile programs. Pyongyang carried out a sixth nuclear test on Sept. 3, which it said was of a hydrogen bomb that can be mounted on an intercontinental ballistic missile, and test-fired missiles over Japanese territory into the Pacific Ocean twice in recent weeks.

© KYODO