The rogue state is not backing down quietly from the threats it made to build a missile capable of destruction.
Instead, Kim Jong Un’s regime is continuing to operate the main existing reactor that provides fuel for its atom bombs while hunting for new parts, the UN nuclear watchdog said in an annual report on Friday.
The move comes despite US President Donald Trump’s praising the North Korean’s leader for backing off on plans to fire missiles toward the US Pacific territory of Guam.
He claimed this was because Kim was “starting to respect” the United States.
Mr Trump said: “And you see what’s going on in North Korea. All of a sudden, I don’t know, who knows, but I can tell you, what I said, that’s not strong enough. Some people said it was too strong. It’s not strong enough.”
North Korea has conducted two nuclear tests and dozens of missile tests since the beginning of last year, defying world powers and raising fears of a conflict breaking out on the heavily militarised Korean peninsula.
A missile test last month put the mainland US in range. Pyongyang later said it had a plan to fire missiles at the US Pacific territory of Guam, while Mr Trump said any threats would be met with “fire and fury”.
It is not clear whether Pyongyang can miniaturise a nuclear bomb enough to fit it on top of such a missile, and it is widely believed it cannot yet protect such a warhead from the heat generated when a missile re-enters the earth’s atmosphere.
But North Korea continues efforts to produce material for nuclear bombs, the International Atomic Energy Agency (IAEA) said in a report to its annual general conference.
The IAEA does not have access to North Korea and monitors its activities mainly by satellite imagery.
The IAEA report said: “There were indications in the LWR (light-water reactor) construction yard of an increase in activities consistent with the fabrication of certain reactor components.
”The agency has not observed indications of the delivery or introduction of major reactor components into the reactor containment building.”
The new reactor is expected to be larger than the current experimental one at Yongbyon.
There was no indication in the past year, however, that the Communist state had used the laboratory near its main reactor where it usually produces plutonium from spent fuel rods, the IAEA said.
It appeared to contradict a recent report by a US think tank that said the lab had operated intermittently.
There were indications the experimental reactor had kept running, the IAEA said.
Its previous report said the reactor had been refuelled in 2015 and those fuel rods would probably be removed two years later.
Friday’s report confirmed the prediction, saying this fuel cycle should last until late 2017.
Even less is known about North Korea’s efforts to produce another material that can fuel nuclear weapons – highly enriched uranium – but the report suggested those had continued at Yonbyon.
The report stated: “There were indications consistent with the use of the reported centrifuge enrichment facility located within the plant.
“Construction work was undertaken on a building which adjoins the reported centrifuge enrichment facility.”