"To cope with the strategic instability in the region and the rest of the world caused by the US unilateral action, the DPRK cannot but reconsider the measures necessary for the improvement of the overall nuclear deterrence posture within the range of its vested sovereign right and possible options," the spokesperson was quoted as saying by North Korean state-run news agency KCNA.
North Korea will not allow the creation of a strategic imbalance in ensuring security on the Korean Peninsula, the spokesperson added.
Last week, the US successfully executed another subcritical experiment to allegedly provide essential data on the behavior of materials used in nuclear warheads, the US Department of Energy's National Nuclear Security Administration said. The authority said that the experiment was consistent with the US's self-imposed moratorium on nuclear explosive testing and did not create a self-sustaining, supercritical chain reaction.