North Korea has been testing a nuclear detonation device “for weeks,” likely in preparation for a nuclear test, a top South Korean security official said Wednesday.

But Kim Tae-hyo, deputy director of the National Security Office (NSO), assessed that a nuclear test is not likely to take place in the next couple days.

South Korea has detected North Korea’s “nuclear detonation experiment for a nuclear test,” Kim said in a background briefing, stating that the experiment has been “sustained for weeks.” 

“Looking at this, it appears that a final preparation phase … is imminent,” Kim said, adding that Pyongyang is