When North Korean leader Kim Jong Un and his South Korea counterpart, Moon Jae-in, meet next Friday, the most important topic on the agenda is the one on which there has been least clarity: denuclearization.
The term has been bandied about in recent weeks, from Seoul to Washington to Beijing, yet there's little agreement on what the term means -- and confusion could lead to trouble in this week's summit as well as the planned meeting between US President Donald Trump and Kim.
South Korean officials and Chinese state media have said Kim is willing to discuss denuclearization on the Korean Peninsula.
On Thursday, President Moon announced North Korea had not raised its long-running demand for the withdrawal of US forces in exchange for giving up nuclear weapons -- an apparent concession that analysts greeted with skepticism.
"North Korea has been saying all the right things ... they want this summit to occur and they're doing what it takes to make it happen," said Adam Mount, a senior fellow at the Federation of American Scientists.
So far, North Korean state media has made no mention of the topic, and public statements by Kim have been vague.
"It is our consistent stand to be committed to denuclearization on the peninsula, in accordance with the will of late President Kim Il Sung and late General Secretary Kim Jong Il," Kim said in Beijing on March 27, according to Chinese state news agency Xinhua.
It elicited a positive response from US President Donald Trump, who said there was now a "good chance" of denuclearization by North Korea.
But are Trump, Kim and Moon talking about same thing when it comes to North Korea giving up its nuclear capabilities?
Denuclearization: What the US and South Korea mean
Over the past decade, denuclearization in North Korea has only ever meant one thing for the United States and South Korea.
"It's called CVID -- complete, verifiable, irreversible dismantlement of the North Korean program," said Josh Pollack, senior research associate at the Middlebury Institute of International Studies at Monterey.
The language has been used consistently by the United Nations Security Council in its resolutions condemning North Korea as far back as October 2006.
"Irreversible," in the practical sense, aims to ensure the current facilities cannot be reactivated after they've been dismantled, Pollack said.
Any denuclearization deal would need to include a series of "verifiable" steps for dismantling North Korea's program, carried out under the eyes of independent observers, former Australian Prime Minister and diplomat Kevin Rudd told CNN in March.
"Unless there is independent monitoring ... any unilateral undertakings by the North Koreans will probably not be worth the paper they're written on," he said.
Inspections could be carried out by an international body such as the International Atomic Energy Agency (IAEA) whose inspectors were previously expelled by North Korea in 2002.
For decades, the US and South Korea have pushed for denuclearization in North Korea.
In 1991, Pyongyang joined Seoul in signing a "joint declaration of the Denuclearization of the Korean Peninsula." Two years later, North Korea pledged it would dismantle its nuclear program in exchange for international aid.
But every time promises weren't delivered and pledges not followed through on both sides, leading to disappointment and suspicion.
Still, the US government appears hopeful the latest round of talks will be different. Trump on Wednesday offered a bullish view, insisting he's positioned to accomplish what his predecessors could not.
However, he said he'd be willing to stand up and leave the highly anticipated summit should the meeting fall short of his expectations.
On South Korea's part, Moon denied on Thursday there was any separation between what the North and the South meant by denuclearization. "I do not think there is any difference in the concept," he said.
Denuclearization: What North Korea means
When North Korean leader Kim Jong Un promised talks on denuclearization in Beijing in March, according to Xinhua, he didn't speak of Pyongyang ending its program. He spoke of "denuclearization on the (Korean) Peninsula."
"To Kim, denuclearization applies to the whole peninsula, which includes the South," David Maxwell, retired US Army Special Forces colonel and a fellow at the Institute of Korean American Studies, told CNN in March, prior to Moon's statement on Thursday.
Experts said Pyongyang has long been expected to push for American military presence across the border to be part of the discussion, a position Pollack said he wasn't sure had changed despite the South Korean's president's remarks.
Although the US hasn't stationed nuclear weapons in South Korea since 1992, Pollack said North Korea considered the US's mere presence on the peninsula a nuclear threat.
"They really are threatened by superior American and South Korean military power, they need nuclear weapons to try and prevent an invasion in their view," Pollack said.
"They feel the need to equate their nuclear program with the (US and South Korean) military alliance and claims the military alliance is a nuclear threat, when there's no real grounds for that."
Experts said North Korea's apparent change of heart on the US military presence in South Korea seemed at best a temporary concession or, at worst, an attempt to drive a wedge between Washington and Seoul.
"The pessimistic interpretation is that Kim is intent on making concession after concession in private to show Moon that he is the reasonable one, with the expectation that Trump will ultimately be unable or unwilling to deliver," Pollack said.
'Pie in the sky'
Experts told CNN the confusion over how much each side was willing to give and what their basic goals were for the summits make a positive outcome harder to see.
Adam Cathcart, an expert on North Korea at the University of Leeds in the UK, said the hopes of some officials in Washington that Kim would willingly give up his nuclear weapons program were "utopian, really pie in the sky."
Speaking to CNN in March, Cathcart said given the ongoing "disdain" the Trump administration had shown for the Iran deal reached during President Barack Obama's administration, it was hard to see a similar, incremental plan getting support in Washington.
The deal removed many of the sanctions on the Iran government, in exchange for the Middle East country getting rid of the majority of its weapons program and uranium -- a key ingredient for nuclear weapons.
The reality, argue analysts, is there simply too much distrust and too little understanding between the two sides to come to an agreement.
"They will affirm the principle of denuclearization as they did in 2005," said Pollack. "And the implementation will be drawn up and never happen," he said.
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