The United States, Japan, and South Korea have agreed to give an "unparalleled" response to a possible nuclear test by North Korea.
"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 on Wednesday, after meeting with Japanese Vice Foreign Minister Mori Takeo, and US Deputy Secretary of State Wendy Sherman.
"We urge (Pyongyang) to refrain," said Sherman, who is on a three-day visit to Japan, adding, "Anything that happens here... has implications for the security of the entire world."
The US and South Korea have been speculating for days that North Korea may be making preparations for a new nuclear test. On Tuesday, South Korean President Yoon Suk-yeol said the North had finished all such preparations.
Washington, Seoul, and Tokyo had previously warned Pyongyang that a new nuclear test would be in violation of United Nations Security Council resolutions.
"We hope indeed that everyone on the Security Council would understand that any use of a nuclear weapon will change the world in incredible ways," Sherman said in a thinly-veiled message to Pyongyang's allies on the Security Council, China and Russia.
North Korea has long been under harsh UN sanctions over its nuclear and missile programs. The US has spearheaded the sanctions and slapped several rounds of its own.
North Korea's leader Kim Jong-un insists that Pyongyang needs to develop its missiles and nuclear weapons as a deterrent in the face of the United States and its allies in the region, where the US has permanent military presence. Both South Korea and Japan host US military bases.