Washington’s point man on North Korea has assessed that the North is ready to conduct a nuclear test at any time.

U.S. Special Representative for North Korea Sung Kim shared his views in a telephone briefing on Tuesday, adding that the regime appears to have completed its preparations for a seventh nuclear test.

Kim declined, however, to guess when the test will be carried out and said the U.S. hopes Pyongyang will refrain from going forward with a test that will make the whole region unstable.

He echoed U.S. Deputy Secretary of State Wendy Sherman’s earlier remarks that the North’s nuclear experiment, if conducted, will be met with a “swift and decisive response,” adding that Washington will closely cooperate with South Korea, Japan and its other allies and partners to respond.

The U.S. official still emphasized dialogue with North Korea, saying it is willing to take a more comprehensive, flexible and open-minded approach to diplomacy should the North show interest in finding a diplomatic path forward.