North Korea is not yet likely to have miniaturized nuclear warheads to mount on ballistic missiles, though it appears to have been developing related technology to a “considerable” degree, Seoul’s Defense Ministry said Thursday.

“They have technology of a considerable level but it is unlikely they are capable of miniaturizing nuclear warheads. In other words, they have not mastered the weaponization process,” ministry spokesman Kim Min-seok said at a regular news briefing.

His remarks run counter to an analysis by Joel Wit, a researcher at the U.S.-Korea Institute of Johns Hopkins University, that the country is believed to have built up to 16 atomic devices ― six to eight of them based on plutonium and four to eight on highly enriched uranium.

Wit, who previously oversaw North Korea affairs at the U.S. State Department, also argued that Pyongyang seems to have acquired the technology to make bombs small enough to fit on its medium-range Rodong missiles, which are capable of striking South Korea and Japan, and on the intercontinental Taepodong-2 missiles.

“Would you be able to make nuclear weapons without succeeding in miniaturizing them?” Kim said.

“(Wit’s assertion) is simply an assumption by some private organization or experts, not substantiated by any evidence. We assess that (North Korea) has yet to secure the technology.”

No signs of another underground blast have been detected from across the border, Kim noted, despite a news report that the communist country is gearing up to detonate an atomic device in May.

“As we’ve repeatedly said, North Korea appears to be ready to go ahead with a fresh test whenever it wants. But it should make a decision, facing a significant level of political pressure including U.N. sanctions,” the spokesman said.

North Korea has conducted three rounds of nuclear tests ― in 2006, 2009 and 2013. Last year, it repeatedly threatened a “new form” of nuclear test in line with its parallel pursuit of nuclear and economic development.

By Shin Hyon-hee (heeshin@heraldcorp.com)