Warning comes amid growing concern that Pyongyang is preparing for its first nuclear weapons test since 2017.
US Deputy Secretary of State Wendy Sherman has said there would be a “forceful” response from the United States, South Korea and the world if North Korea were to conduct a nuclear test.
“Any nuclear test would be in complete violation of UN Security Council resolutions [and] there would be a swift and forceful response to such a test,” Sherman told reporters on Tuesday after talks with her South Korean counterpart, Cho Hyun-dong, in Seoul.
Sherman added: “The entire world will respond in a strong and clear manner. We are prepared.”
There are growing concerns that North Korea, which has conducted an unprecedented number of missile launches this year, will soon test a nuclear weapon for the first time since 2017.
The International Atomic Energy Agency (IAEA) has said that North Korean moves to expand key facilities at its main nuclear site at Yongbyon continue to advance.
“A roof has been installed on the annex to the reported Centrifuge Enrichment Facility, so the annex is now externally complete. Near the light water reactor (LWR), we have observed that the new building that had been under construction since April 2021 has been completed, and construction has started on two adjacent buildings,” IAEA Chief Rafael Grossi said in his quarterly statement to the Board on Monday.
He also noted that at Punggye-ri, North Korea’s nuclear test site, there were indications that one of the passages known as adits had been reopened, possibly in preparation for a nuclear test. The site was dismantled in 2018 following a summit between North Korean leader Kim Jong Un and then South Korean President Moon Jae-in.
“The conduct of a nuclear test would contravene UN Security Council resolutions and would be a cause for serious concern,” Grossi said.
During her visit to Seoul, Sherman reiterated that the US administration remained open to talks.
Discussions on denuclearisation have been stalled since the collapse of a high profile summit between Kim and then US President Donald Trump in Vietnam in 2019.
“The United States harbours no hostile intent towards the DPRK. We continue to urge Pyongyang to cease its destabilising and provocative activities and choose the path of diplomacy,” she said, referring to North Korea by its formal name.