US President Donald Trump and North Korean leader Kim Jong Un are meeting today for their second summit, betting their personal relationship can break a stalemate over the North's nuclear weapons and end more than 70 years of hostility.
Despite little progress toward his stated goal of ridding North Korea of its nuclear weapons since first meeting Kim in Singapore last year, Trump has said he is fully committed to his personal diplomacy with Kim.
Trump said late last year he and Kim "fell in love", and on the eve of his departure for the second summit said they had developed "a very, very good relationship".
Whether the bonhomie can move them beyond summit pageantry to substantive progress on eliminating Pyongyang's nuclear arsenal that threatens the United States is the question that will dominate their talks in the Vietnamese capital of Hanoi.
"Vietnam is thriving like few places on earth. North Korea would be the same, and very quickly, if it would denuclearise," Trump said on Twitter.
"The potential is AWESOME, a great opportunity, like almost none other in history, for my friend Kim Jong Un. We will know fairly soon - Very Interesting!"
Trump and Kim will meet at the Metropole Hotel at 6.30pm (7.30pm in Malaysia) for a 20-minute, one-on-one chat followed by a dinner with aides, the White House said.
The elegant interior of the 118-year-old Metropole thronged with security and diplomatic personnel from both sides - some snapping pictures - as hotel staff made final preparations.
Tomorrow, the two leaders will hold "a series of back and forth" meetings, the White House said. The venue for those meetings has not been announced.
In Singapore, they pledged to work toward denuclearisation and permanent peace on the Korean peninsula. North and South Korea have been technically still at war since their 1950-53 conflict, with the Americans backing the South, ended in a truce, not a treaty.
The Singapore meeting - the first between a sitting US president and a North Korean leader - ended with great fanfare but little substance over how to dismantle North Korea's nuclear weapons and ballistic missiles.
Both sides are likely to feel pressure to agree on specific measures this time - what concrete steps North Korea will take to give up the weapons, and what the United States will offer in return.
While the United States is demanding that North Korea gives up all of its nuclear and missile programmes, the North wants to see the removal of a US nuclear umbrella for South Korea.
US intelligence officials have said there is no sign North Korea will ever give up its entire arsenal of cherished nuclear weapons, which it sees as its guarantee of national security, while analysts say it won't commit to significant disarmament, unless punishing US-led economic sanctions are eased.
Trump has held out the prospect of easing them if North Korea does something "meaningful".
Any deal will face scrutiny from American lawmakers and other sceptics who doubt North Korea is really willing to give up the weapons, and who worry a compromise could squander US leverage and undermine regional interests.
Trump scoffs at the doubters, citing a freeze in North Korea's nuclear and missile tests since 2017, and saying the United States would have gone to war with North Korea if he had not been president.
"The Democrats should stop talking about what I should do with North Korea and ask themselves instead why they didn’t do 'it' during eight years of the Obama Administration?" he said on Twitter.
Whatever the outcome, the summit should boost Kim's bid to end his country's pariah status and cement his place, both on the world stage and at home.
As the young, third-generation leader of one of the world's most impoverished and isolated nations, living under punishing sanctions, Kim will again stand as an equal to the president of the world's most powerful country.
For Trump, a deal that eases the North Korean threat could hand him a big foreign-policy achievement in the midst of domestic troubles.
While Trump is in Hanoi, his former personal lawyer Michael Cohen (photo) is testifying before US congressional committees, with the president's business practices the main focus.
Anticipation has also been rising about the impending release of Special Counsel Robert Mueller's report on Russian interference in the 2016 US election, though a senior US Justice Department official said last Friday that it would not come out this week.
In the run-up to the summit, Trump has indicated a more flexible stance, saying he is in no rush to secure North Korea's denuclearisation.
The two sides have discussed specific and verifiable denuclearisation measures, such as allowing inspectors to observe the dismantlement of North Korea's Yongbyon nuclear reactor, US and South Korean officials say.
US concessions could include opening liaison offices, declaring an end to the technical state of the Korean War or clearing the way for some inter-Korean projects.
Vietnam, relishing its role as mediator, could serve as a model for North Korea as it seeks a path out of isolation.
Vietnam normalised ties with old battlefield foe the United States in 1995 after decades of Cold War mistrust, and its "doi moi" reforms have transformed its economy.
Trump met Vietnamese President Nguyen Phu Trong at the grand, colonial-era presidential palace, and said both he and Kim felt good about holding their summit in Vietnam. Trump also said the United States and Vietnam would be signing trade, including one involving Boeing.
Vietnamese carrier Bamboo Airways is due to sign a deal with Boeing to purchase 10 planes on the sidelines of the summit, an airline executive said on Sunday.