A further nuclear test by North Korea would be "incredibly concerning" and everyone is "holding their breath", said the head of the UN nuclear watchdog.
The United States, Japan and South Korea all warned on Wednesday that an "unparalleled" scale of response would be warranted if North Korea conducts a seventh nuclear bomb test.
And now the International Atomic Energy Agency (IAEA) Director General Rafael Grossi said a seventh nuclear test would be further "confirmation of a programme which is moving full steam ahead in a way that is incredibly concerning."
He stated: "Everybody is holding its breath about this.
"Further tests, of course, means that they are refining the preparations and the construction of their arsenal."
He told reporters in New York that the IAEA is following North Korea's actions very closely, and added that "we hope it doesn't happen, but indications unfortunately go direct in another direction."
The United States and its allies believe North Korea could be about to resume nuclear bomb testing for the first time since 2017.
"We agreed that an unparalleled scale of response would be necessary if North Korea pushes ahead with a seventh nuclear test," South Korean First Vice Foreign Minister Cho Hyun-dong told a news conference in Tokyo.
Cho was speaking alongside his Japanese and US counterparts, Vice Foreign Minister Takeo Mori and Deputy Secretary of State Wendy Sherman.
The United States and its allies have offered few details on what new measures they might take, and observers say they have few good options for preventing a new test.
For the first time since North Korea began testing nuclear weapons in 2006, China and Russia this year vetoed a US-led push for additional United Nations Security Council sanctions, and stepped-up allied military drills have only been met by more North Korean tests and exercises.
"We urge (North Korea) to refrain from further provocations," Sherman said, calling them "reckless and deeply destabilising for the region.
"Anything that happens here, such as a North Korean nuclear test ... has implications for the security of the entire world," she said, sending a thinly veiled message to Pyongyang's supporters, China and Russia, in the UN Security Council.
