US President Donald Trump, speaking to US broadcaster Fox News on Sunday evening, said Washington had sought, during a February summit with North Korean leader Kim Jong Un, to shutter five nuclear sites, but Pyongyang was only willing to close two.

Trump’s comments were among the clearest indications yet on why that summit, held in Hanoi, Vietnam, broke up without any agreement being reached. The future of further talks – and indeed, the future of North Korea’s promised denuclearization process – have been uncertain ever since.

“When I left Vietnam where we had the summit, I said to Chairman Kim … And I think very importantly I said, ‘Look, you are not ready for a deal because he wanted to get rid of one or two sites,” Trump said in televised comments. “But he has five sites … I said, ‘What about the other three sites?’ That is no good.”

Previously, it had been revealed that Kim had put one facility – his main nuclear complex, the Yongbyon Nuclear Scientific Research Facility, some 100 kilometers North Korea Pyongyang – on the table. But according to Trump’s interview, there may have been one other facility Kim was willing to give up.

However, Trump offered no further clarity in his interview, raising a new slew of questions.

Even so, the number offered suggests how far apart the two sides were – and could provide a starting point if talks resume.

“The new information here is the specification of the number of nuclear sites,” Go Myong-hyun, a North Korea watcher at Seoul think tank the Asan Institute told Asia Times. “We assume the US government has pretty full information … if that is really the case, it is a good starting point for negotiations. We know the upper boundary.”

What constitutes Yongbyon?

North Korea’s nuclear sites are necessarily shrouded in mystery. The secretive state is known to have two programs producing weapons-grade fissile materials – a processed plutonium-based program and a highly enriched uranium (HEU) based program.

There are two complicating factors. Firstly, the second program may be dispersed over multiple sites, and secondly, it is not entirely clear to researchers what or where the limits of Yongbyon are, which has been expanded since six-party denuclearization talks foundered in 2008.

The latter point suggests that it is not clear whether Kim, in his reported offer to dismantle Yongbyon, was referring to the facility itself, or to an extended complex of facilities in the Yongbyon area – which could, feasibly, explain the two sites Trump mentioned.

“In the greater Yonbyon area there are meant to be dozens of facilities related to the program,” said Chad O’Carroll, CEO of North Korea Risk Group. “There are many other facilities in Yongbyon, so it is very hard to know what Trump meant by ‘five.’”

Moreover, there are known to be both plutonium and uranium-based programs at Yongbyon. “The big question is, ‘what does Yongbyon represent as far as the number five goes?” added O’Carroll. “It could represent two or three.”

In January, Stephen Biegun, the US special envoy to North Korea,  said Kim had committed “… to the dismantlement and destruction of North Korea’s plutonium and uranium enrichment facilities.” Biegun added: “This complex of sites that extends beyond Yongbyon represents the totality of North Korea’s plutonium reprocessing and uranium enrichment programs.”

Site after site

What remains opaque is whether the US has positively identified facilities not in the immediate Yongbyon area. That seems likely. During his post-summit press conference, Trump made clear that his team had shown the North Korean delegation in-depth intelligence about their programs.

An alleged HEU facility was tentatively identified southeast of Pyongyang by a team of researchers working at the Center for Nonproliferation Studies at the Middlebury Institute of International Studies in the United States in July 2018. The researchers, writing in The Diplomat, said the site had been confirmed as Kangson, a covert HEU facility, by a US intelligence source.

Given the tactical need for North Korea to disperse sites that could become targets for potential US strikes, there may be more.

“There are known to be other hidden uranium enrichment faculties [beyond Yongbyon], and Trump is presumably referring to those,” said O’Carrol. “It makes no sense to have all those uranium enrichment facilities in one place.”

Finally, it is not clear whether Trump was referring simply to nuclear processing facilities. Other facilities that would be of critical interest to the United States would include storage sites for fissile materials, facilities where actual nuclear weapons are engineered and military bases were atomic warheads are deployed.

“My guess is that [North Korea has] an inner limit on how much they want to produce, as maintaining a nuclear arsenal is pretty costly,” said Go. “The logic is they are probably ramping up production of warheads and will give up what they don’t need – which are the production and storage sites. They will never give up the weapons.”

Still, given Trump’s lack of detail and the speculation required to analyze it, one expert dismissed his televised comments entirely.

“I have no opinion as to those numbers, it is irrelevant,” Chun In-bum, a retired South Korean general, told Asia Times. “It is very difficult to know how many really credible nuclear facilities there are – I would not even venture to try to guess.”