There are concerns that the US President's unorthodox leadership style could cause tensions with North Korea to flare-up during a summit that's meant to bring peace.
The upcoming meeting was briefly cancelled after Donald Trump said the North Koreans were showing "tremendous anger and open hostility", but it's now back on, with preparations in Singapore underway.
Waikato University international relations expert Alexander Gillespie says history shows that usually by now, we'd know exactly what Mr Trump and North Korean dictator Kim Jong-un would be discussing, and what's on offer from both sides - but it remains a mystery.
"What we hope is on the bit of paper is there is going to be a complete denuclearisation of the Korean peninsula," Prof Gillespie told Newshub.
"The question though is whether North Korea really wants to give up its nukes - it's promised to do that twice before, and twice before it's broken its promise."
The meeting is only nine days away. Prof Gillespie says if it does go ahead, it could go sour quickly.
"Both men are very volatile and they are known to take offence quite easily, use extreme rhetoric and threaten each other if things go wrong, at very short notice."
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In the past, Mr Trump and Mr Kim have traded insults - the US President usually through Twitter, and Mr Kim, through North Korea's state media outlets.
Mr Trump has called Mr Kim a "maniac", "madman" and "Rocket Man", warned of "fire and fury" and boasted about the size of his "nuclear button".
In turn, the North Koreans have called Mr Trump a "mentally deranged US dotard" and regularly threatened to strike its much larger enemy.
Prof Gillespie told Newshub in May that if the summit results in an official end to the Korean War and denuclearisation of the peninsula, Mr Trump and Mr Kim should "absolutely" win the Nobel Peace Prize.
But he gave that a 10-to-one chance of happening.
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