Trump, who has pitched himself as the ultimate negotiator, has focused on ambitious deals as president but has struggled with the fine print.
Yet, in the lead-up to the Singapore summit, Trump and Bolton have gratuitously referred to the "Libya model" in the specific context of North Korea.
The biggest sticking point appears to be the definition of denuclearization: USA officials have repeatedly said they expect North Korea to accept "complete, verifiable, irreversible disarmament", while Pyongyang is seeking a phased process that could include a reduced US military presence in the region. South Korea's national security adviser put the chance of the summit taking place at 99.9 percent.
The North Koreans have threatened to pull out of the talks with Trump, blaming what they term are demands by the United States for "unilateral nuclear abandonment".
Mr Pence said in a Fox News interview that such a move would be a "great mistake" by the North Korean leader.
"Specialists must be dispatched to the site to collect samples from past tests and analyze them to determine explosive power and materials used", Albright told the Mainichi Shimbun.
Still, some news reports suggested Trump, or at least his aides, may be having second thoughts about the U.S.
Additionally, if North Korea truly has completed its nuclear program, as it says it has, then it no longer needs an active test site anyway.
The meeting comes as reporters travel by plane from Beijing to North Korea to witness the dismantling of the Punggye-ri nuclear test site, which North Korea has said will take place between May 23 and 25.
This implies that the main US objective is to eliminate North Korea's long-range missile capability. It was Moon's government that delivered the initial invitation from Kim for a meeting, and South Korea has been pushing the USA toward a peaceful resolution to the nuclear crisis.
The summit ended with a joint declaration that both countries are committed to denuclearization and officially ending the war 65 years after the armistice. "So the North is tying any improvement in inter-Korean relations to the success of the North Korea-US summit", said Ko Myong-hyun, a research fellow at the Asan Institute for Policy Studies.
Lee, of the Wilson Center, contends "the North Koreans have skillfully played the situation by manufacturing an awkward moment between Moon and Trump just before their May 22 meeting".
Kelly said the Moon administration will be "very concerned about the possibility of backsliding into "fire and fury". The White House turned heads this week with the release of a commemorative "challenge coin" for the summit, featuring profile engravings of Trump and Kim for the "peace talks". South Korean reporters were unable to join the trip because the North denied their entry in protest at an ongoing Seoul-Washington military drill and an anti-Pyongyang speech in Seoul by a high-ranking North Korean defector.
USA officials said preparations for the summit were still underway despite recent pessimism - and privately suggested there would be additional public maneuvering as both sides seek to maximize their leverage.
US President Donald Trump and South Korean President Moon Jae-in shake hands at a news conference at South Korea's presidential Blue House in Seoul, South Korea, November 7, 2017.
"There's always a temptation to see North Korea as a pawn in China's game but the North Koreans have their own play here and Kim Jong Un's not just going to do Xi Jinping's (bidding)", said John Delury, associate professor at Seoul's Yonsei University.
Trump administration officials have also grown concerned that the President is overly eager for the summit to take place, increasing Kim's leverage should the talks take place, United States officials and a source close to the administration said.