South Korea’s defense ministry said Tuesday that North Korea appeared to have achieved a “significant” level of technology to miniaturize a nuclear device to be fitted on the tip of a missile.
The ministry made the warning in a white paper due to be released later Tuesday, although defense officials said the nuclear-armed North has yet to demonstrate its miniaturization capacity.
“North Korea’s capabilities of miniaturizing nuclear weapons appear to have reached a significant level,” the ministry said in a statement.
Pyongyang has conducted three nuclear tests, most recently in February 2013.
The defense ministry said the North had probably secured some 40 kilos (88 pounds) of weapons-grade plutonium by reprocessing spent nuclear fuel rods, and that it is working on a highly enriched uranium program.
Pyongyang mothballed the five-megawatt reactor at its main Yongbyon nuclear complex in 2007 under an aid-for-disarmament accord, but began renovating it in mid-2013. The facility is the country’s main source of weapons grade plutonium.
The North is presumed to have the capacity to developing missiles that could threaten the US mainland, through a series of long-range missile tests, the defense ministry said.
In 2012, Pyongyang demonstrated its rocket capabilities by sending a satellite into orbit, but it has yet to conduct a test that would show it had mastered the re-entry technology required for an inter-continental ballistic missile (ICBM).