From scathing insults to a high-stakes summit: Can Trump and Kim make a deal in Singapore?

Singapore, the city state has become Singapore, the summit state. The tone ahead of Tuesday's talks between the U.S. president and the North Korean leader has been positive, but the outcome is far from clear.

U.S. president says Singapore summit is a 'one-time shot' for North Korean leader

Armed police officers patrol outside the Shangri-La hotel where U.S. President Trump will stay ahead of the U.S.-North Korea summit in Singapore. (Ted Aljibe/AFP/Getty Images)

Singapore, the city state has become Singapore, the summit state. Cleaned up, locked down and ready to make history.

The key players have arrived, with North Korea's Kim Jong-un touching down Sunday after his longest plane journey since taking power.

Kim only started meeting with foreign leaders in recent months, slowly shedding a reputation as the reclusive ruler of the so-called Hermit Kingdom after summits with the Chinese and South Korean presidents.

Now he's in Singapore, ready to negotiate with U.S. President Donald Trump. But what will happen is far from clear, as leaders with a history that includes both raging insults and conciliatory gestures try to de-escalate nuclear tensions and decades of discord.

The tone heading into the meetings is positive, but the risk that things will go awry is also very real.

"The worst case scenario would be if President Trump came into the summit and presented an ultimatum demanding complete and verifiable denuclearization," said James Trottier, a former Canadian diplomat who led several missions to Pyongyang. "That would be rejected and Trump would walk out."

Setting the stage

On his way to Asia from the G7 meeting in Canada, Trump said he was embarking on a "mission of peace," predicting he'll know "within the first minute" if Kim is serious about negotiating. Their meeting is expected to begin Tuesday with a one-on-one session — just Trump and Kim and their personal interpreters.

"I think I'll know pretty quickly whether or not, in my opinion, something positive will happen," said Trump. "And if I think it won't happen, I'm not going to waste my time."

Trump arrived in Singapore calling the summit a "one-time shot" for Kim, who is being urged to abandon his weapons program and normalize relations with the rest of the world in exchange for unspecified "protections" from the U.S. North Korea has long worried about an American invasion and justifies its nuclear buildup as a way to defend itself.  

People try to get a peek of the vehicle carrying North Korean leader Kim Jong-un on Saturday in Singapore ahead of the summit between the North Korean leader and Trump. (Tyrone Siu/Reuters)

The North Korean leader has in recent months been trying to shift his image from reclusive tyrant to smiling statesman. But his ruthlessness at home and a human rights record that UN investigators have described as "harrowing" have left many unconvinced about his sincerity.

Kim remains very much a mystery to most, including the curious Singaporeans who try to catch a glimpse as his armoured motorcade zooms past.

Deals or demands?

As the final preparations for the summit were being made, some veteran diplomats warned against an all-or-nothing approach from the U.S.

Observers in the region warn that ultimatums over denuclearization could make military confrontation between the U.S. and North Korea even more likely, a situation Zhao Hai from China's Academy of Social Sciences described as a "down-spiral of security" that could turn into a nuclear "nightmare."

Most experts say North Korea's nuclear program is so large and the process of dismantling it is so complex that the only way to succeed is to engage Pyongyang in gradual negotiations that could stretch for years.

If a deal on nuclear weapons is made, verification would also be a big challenge. And even if North Korea agrees to dismantle all of its nuclear weapons, what's to say it won't make more now that it has the formula?  

Recently, Trump himself tried to lower expectations for the talks in Singapore.

President says he will meet with North Korea in Singapore. 0:29

"Wouldn't it be wonderful if we walked out and everything was settled all of a sudden from sitting down for a couple of hours?" Trump said after a meeting with North Korean envoy Kim Yong-chul at the Whitehouse. "No, I don't see that happening. But I see over a period of time."

Trump has even floated the idea of extending this week's summit for a second day, and maybe inviting Kim to the United States for further meetings.

'Little rocket man' meets the 'dotard'

But just last year, Trump described the North Korean leader as "little rocket man," and warned of a U.S. military attack full of "fire and fury." Kim had his own harsh words, calling the president a "mentally deranged U.S. dotard."

That tension meant Trump surprised both foreign allies and his own advisers when he accepted Kim's invitation to this summit in April. He surprised them again a couple of weeks ago when he called it off,  leaving the region worried about dangerous consequences.

The cancelled meeting was ultimately resurrected, and now the pair are less than a day away from holding historic talks. Trump and Kim come from very different backgrounds and ideologies, and at 71, Trump is about twice as old as the North Korean leader. But they share a similar hands-on approach, with decisions based on their own personal views —sometimes even their whims.

Trump has said he doesn't think he needs much preparation for this summit. On the other hand, American and South Korean officials have described Kim as well versed on the issues and very clear on what he wants to achieve: a relaxation of punishing economic sanctions in return for real or maybe just vaguely promised denuclearization.

Trump, seen here arriving in Singapore, has said his goal is denuclearization of North Korea. But how far he hopes to get in the upcoming talks is not clear. (Win McNamee/Getty Images)

Paul Haenle worries there's a preparation gap that has left Trump — and the U.S. —  at a disadvantage. Haenle served as the White House representative at negotiations with North Korea under U.S. President George W. Bush, and as a national security advisor in the Obama administration. He's now the director of the Carnegie Tsinghua Center, a thinktank in Beijing.

"There is the risk that President Trump, being so desperate to achieve a deal, to get the Nobel Peace prize, may just put things on the negotiating table that over the long-term will actually undermine America's interests," Haenle said.

Perhaps he'll offer to withdraw the 28,000 American troops stationed in South Korea, Haenle said, or to pull back the so-called nuclear umbrella of protection Washington offers allies South Korea and Japan.

But the truth is, no one knows what Trump will do in tomorrow's negotiations with Kim — just as no one knows how Kim will respond.

Two big enigmas, with their fingers on nuclear buttons.