GOYANG, South Korea (WASHINGTON POST) - Forget about Kim Jong Un, the nuclear-armed tyrant threatening to nuke Washington and take out US military bases in Asia. Here comes Kim Jong Un, the international statesman.

On Friday morning, the 34-year-old leader of North Korea, a man widely predicted seven years ago to be incapable of keeping control of the world's most authoritarian state, walked across the line that has divided the Korean Peninsula since 1953.

It marked the start of a day of inter-Korean talks and camaraderie that would have been unimaginable just a few months ago.

And it's a sharp turnaround for a man who, as 2018 opened, was bragging about having a nuclear button on his desk and nuclear weapons that had the entire United States within range.

"He's the master of the bold gesture," said Dr Gary Samore, a nuclear non-proliferation expert at Harvard's Kennedy School who served on President Barack Obama's National Security Council.

"We've almost forgotten the (allegations) that he had his half brother killed with a chemical weapon just last year and that he had his uncle ripped apart with antiaircraft guns."

Indeed, the image of Kim presented by the South Korean government was nothing but positive in the lead-up to Friday's historic summit.

Local media outlets stayed on message by broadcasting photos of a constantly smiling Kim.

With his inaugural trip to Beijing to see President Xi Jinping last month, his summit on Friday with South Korean President Moon Jae In and his invitation to President Donald Trump, Kim is presenting himself as a legitimate leader with global standing.

It's quite a metamorphosis.

"He's not just some young buck, some flashy guy," said Balbina Y. Hwang, a North Korea specialist at Georgetown University who worked in the State Department after the 2005 denuclearisation agreement with North Korea.

"I think everybody has totally underestimated him."

Gone are the belligerent threats and photos with huge missiles of 2017.

Gone are the palpable fears in Washington, Seoul and Beijing that the Trump administration might actually go ahead with a military strike to give the North Korean regime a "bloody nose".

Now it's all about working together to come up with a deal everyone can live with - a change driven almost entirely by Kim's sudden pivot toward diplomacy.

This, most analysts say, is the result of a combination of Trump's "maximum pressure" campaign and the North Korean leader's increased confidence now that he has a credible nuclear deterrent.

Wendy Sherman, a former US undersecretary of state with a long history of dealing with North Korea, said that Kim had proved himself to be a tactical and manipulative leader.

"I think it was a smart move to say to the South Koreans that he would meet with Trump and will talk to him about denuclearization, and to let them deliver the news and get this process underway," she said.

"That played into the Korean identity." The South Korean government - which has a strong preference for the diplomatic option, given that the military option could lead to mass carnage in its capital - has said that Kim is prepared to discuss denuclearization and that he will not insist on the standard North Korean condition that U.S. troops be withdrawn from the southern half of the peninsula.

Kim's statement on the matter suggested that he might be willing to freeze his program - now that he has a thermonuclear bomb and an advanced missile technically capable of reaching all of the United States - but gave no indication that he was prepared to relinquish the hard-won weapons."Kim Jong Un has given us quite a few surprises," said Ji-young Lee, professor of Korean studies at American University.

But it's too early to tell whether this is a sign of a fundamental shift, she said."My sense is that it is still at the level of tactics," Lee said. "We shouldn't get too excited about it signalling a change in policy, but I think it has the potential to lead to a more fundamental transformation." The composition of Kim's entourage for Friday's talks suggests that the North Korean leader, like his South Korean counterpart, sees them as a prelude to a summit with Trump.

In the group are Ri Su Yong, the former foreign minister, and Ri Yong Ho, the current one, as well as several top military officials."North Korea appears to be considering not only the inter-Korean summit but also the subsequent North-U.S. summit and efforts for international cooperation," Im Jong-seok, Moon's chief of staff and head of the summit preparation committee, told reporters Thursday.

Kim's sister, Kim Yo Jong, who visited the South in February and delivered the summit invitation to Moon, is also part of the delegation.

But shaking hands and planting trees are one thing. Coming up with an agreement that can form a springboard to substantive denuclearization talks with Trump is quite another.

Many analysts have voiced concerns that expectations for Friday's summit - and especially for the summit with Trump - have been wildly inflated and are now completely unrealistic.

"We all know that this is a farce," said Harvard's Samore. Kim "has no intention of giving up his nuclear weapons."

The North Koreans also are not likely to accede to a key part of the denuclearization process: inspection and verification.

"This is all good, but it's the icing on the cake," Sherman said of Kim's recent signals.

"It's not the cake. The cake is him giving up his weapons, and the first step toward that is letting in inspectors and letting them see what he's got and what needs to be secured. That's going to be difficult."

That means North Korea will want to keep up the pretense that it's serious about denuclearization for as long as possible.

"The North Koreans have a strong incentive to drag this out," said Samore, who also was involved in the Iran nuclear deal. "The sanctions are going to get weaker. China and Russia are not really going to enforce them if it looks like North Korea is playing along." Already the new tone coming out of Pyongyang has led to a sharp shift in mood in the region.

China, which had been worried that Trump was serious about military strikes and joined his "maximum pressure" campaign to try to stave them off, already is easing up on sanctions, according to several people familiar with the border trade.

Checks on exports to and limitations on imports from North Korea already are being loosened, a Chinese academic said on the condition of anonymity to discuss sensitive government policy.

South Korean media outlets have reported that Kim presented Xi with a list of demands while he was in Beijing last month - the aid and trade concessions he wants for going along with the diplomatic process. This has not been confirmed by Beijing.

Still, given the course that North Korea was on last year, a year in which it made astonishing advances in both its nuclear program and its missile systems, the fact that all the players are now on a diplomatic path is being welcomed, even by former Obama administration officials.

"The reason I support the president giving this a chance is because North Korea believes that only leaders can make decisions," said Sherman.

Samore agreed. "I'm very sceptical, but I think it's worth a try," he said. "And it's certainly better than talking about giving Kim Jong Un a 'bloody nose.' "