TOKYO/SEOUL (BLOOMBERG) - Kim Jong Un told the world this month that North Korea took steps to stop making nuclear weapons in 2018, a shift from his earlier public statements. The evidence shows production has continued, and possibly expanded.

Satellite-imagery analysis and leaked American intelligence suggest North Korea has churned out rockets and warheads as quickly as ever in the year since Mr Kim halted weapons tests, a move that led to his June summit with United States President Donald Trump.

The regime probably added several intercontinental ballistic missiles (ICBMs), nuclear proliferation analysts say, with one arms control group estimating that Mr Kim gained enough fissile material for about six more nuclear bombs, bringing North Korea's total to more than 20.

"There is no indication that their nuclear and missile programmes have slowed or paused," said Ms Melissa Hanham, the director of the One Earth Future Foundation's Datayo Project and an expert in using satellite imagery and other publicly available data to analyse weapons proliferation. "Rather, it has reached a new stage."

Recent reports have shown that North Korea continued to operate two suspected uranium enrichment facilities - one near its long-established Yongbyon nuclear centre and another location suspected of being a gas centrifuge site.

In July, US Secretary of State Michael Pompeo acknowledged in Senate testimony that North Korea was still producing fissile material.

Other reports suggest North Korea bolstered its arsenal in the run-up to the Trump summit and still runs a plant believed to have produced Mr Kim's first ICBMs capable of reaching the US homeland.

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They say the regime recently expanded a factory probably making engines for new, easier-to-hide solid-fuel rockets and enlarged an underground base for long-range missiles.

The reports underline what's at stake as Mr Trump considers holding a second summit with Mr Kim, which the US President says could come "in the not-too-distant future".

While Mr Trump has credited Mr Kim's decision to halt weapons tests and dismantle a few testing facilities with preventing a war in the Western Pacific, those moves haven't prevented North Korea from building new weapons out of sight that could threaten the US.

FORTIFYING ARSENAL

Scepticism remains about Mr Kim's denuclearisation pledges, including his assertion in a New Year's speech that he agreed in 2018 to "neither make and test nuclear weapons any longer, nor use and proliferate them".

A year ago, Mr Kim ordered the mass production of warheads and ballistic missiles after suspending weapons tests following the launch of an ICBM capable of reaching the entire US - the last of more than 40 conducted in a 24-month span.

Non-proliferation analysts say Mr Kim's strategy appears to be quietly fortifying the arsenal he has while creating the diplomatic climate necessary for North Korea to get sanctions lifted and be tolerated as a nuclear state.

The stalled nuclear talks with the Trump administration have given Mr Kim the space to perfect the technologies needed to strike the US.

Analysts say it's only a matter of time before he acquires a targeting system and a re-entry vehicle capable of delivering a warhead safely through the atmosphere.

"I don't know of a country that has produced an ICBM and found that building a re-entry vehicle to be a substantial barrier," said Mr Jeffrey Lewis, a specialist on proliferation at the Middlebury Institute of International Studies in Monterey, California.

Mr Lewis and his colleagues produced several reports showing Mr Kim's continued weapons development last year, identifying the probable site of a covert uranium-enrichment facility north of Pyongyang and an expanded missile base near the Chinese border.

TARGET LIST

In recent days, Mr Kim has also made clear that any disarmament deal with Mr Trump would also require removing the US' nuclear-capable planes and warships from the region.

He has shown little interest in declaring his nuclear assets as sought by US officials, with state media last month comparing it to handing over a target list.

Without disclosures and inspections, it is impossible to know exactly what weapons North Korea possesses. The secretive regime has for decades relied on deception and a vast network of tunnels and clandestine facilities to hide the components of its nuclear arms programme from government spy agencies, let alone commercial satellites.

Mr Pompeo told Fox News last Friday that international verification of North Korea's denuclearisation remained the administration's goal as it works to secure a second summit.

'THIS KNOWLEDGE IS DECLINING'

"Reducing the threat from North Korea, whether that's by our success to date in stopping their missile testing, stopping their nuclear testing, those are the important elements," he said. "We've got to get to full and final denuclearisation."

An analysis of satellite imagery published by the 38 North website on Jan 9 showed that the Yongbyon Nuclear Scientific Research Centre, which Mr Kim suggested he might dismantle in exchange for US concessions, remains operational and well maintained.

While the main facilities do not appear to be working, the uranium enrichment plant was a possible exception.

Inspectors say Mr Kim's nuclear programme has reached a stage where it can progress without obvious tests, making it even more difficult to monitor.

The International Atomic Energy Agency (IAEA) underscored that concern in an August report, saying "knowledge of the DPRK's nuclear programme is limited and, as further nuclear activities take place in the country, this knowledge is declining".

"They don't need to test their ICBMs because they are satisfied with the performance," said Ms Hanham, who worked at the Middlebury Institute until November. "Instead, they are following Kim Jong Un's order to mass produce nuclear weapons and the missiles need to deliver them."

How many nuclear warheads North Korea holds is also unknown.

The non-partisan Arms Control Association estimated last year that the regime possessed at least 15 bombs and was churning out enough fissile material to produce six to seven more annually.

"But there is a high degree of uncertainty surrounding these estimates," the Arms Control Association said. By 2020, it could have anywhere from 20 to 100 warheads, potentially exceeding Israel's 80 estimated bombs.

A comparison to Israel may be apt, since the country's weapons programme is tolerated by the international community in part because it stays out of sight. Mr Kim appears to want this sort of "opacity" for his own arsenal, according to Mr Lewis from the Middlebury Institute.

Meanwhile, the international sanctions regime that Mr Kim blames for stifling efforts to develop his impoverished country appears to be doing little to prevent North Korea from building more missiles and warheads. He only needs enough money and material to build a few ICBMs a year to cement his country's status as a nuclear power.

"While the sanctions may put a squeeze on the economy, they are not harming the weapons programme," Mr Lewis said. "There hasn't been any significant political or economic pressure in the past year that would curtail North Korea's weapons programme."