Speaking at the Sydney Writers' Festival on Friday, Pusan National University political science professor Robert Kelly — also known as "BBC Dad" — said the summit was an "unnecessary risk" that would "probably be a bust".
"The ideological and strategic divisions between the two sides are so wide that it's almost impossible to bridge them in nine weeks," he said. "It's just not doable."
He said it was "obvious" Trump was going to "wing it", rather than research beforehand, adding that a good outcome for the West was very unlikely.
So, why bother with the meeting at all then?
Prof Kelly suggested it was a quick decision fuelled by Trump's ego — a decision that could ultimately prove fatal for relations.
"The President says, 'This is a unique moment, I'm meeting with North Korea, which no other American president has ever done', but that's actually not unique. The North Koreans have wanted to meet with a US president going all the way back to the 1970s.
"Why? Because North Korea's a tin pot dictatorship, and meeting the leader of the free world is automatically legitimacy-granting.
"It symbolises that you're a real country and not a backward, feudal, Orwellian fiefdom, which North Korea is."
Prof Kelly said a meeting with North Korea will help them, but that the West will gain nothing from it.
"We don't want to legitimise North Korea … and if we're going to, we at least ought to get something from it. Donald Trump gave that away for nothing. That's why I'm so concerned.
"We've got a President who agreed to do this, who doesn't understand the issues, who agreed to it 45 minutes after it was proposed to him — what happens when they meet one-on-one?"
Filmmaker Anna Broinowski interjected and said: "They get peace. Good! They've been trying for 65 years. Maybe Trump's the great disrupter in all this?
"Just because America doesn't like North Korea's ideology, doesn't mean it doesn't have a legitimate claim to being a country."
Prof Kelly said later he supported a dialogue between the US and North Korea, but did not backtrack on his concerns.
"I just don't believe this President is the right person to do that," he said. "I'm concerned about this President and his seeming insistence that he run this himself.
"The latest rumour is he wants to speak to Kim Jong-un alone — just the two of them and their translators. Who knows what he's going to say? Seriously."
He also warned that a final peace deal that "institutionalises and accepts (North Korea's) existence … will continue the gulag state that it is".
"A peace treaty will be brought on the backs of the suffering and pain of the North Korean people, and that is the single biggest reason we shouldn't do it."
Last week, South Korean President Moon Jae-in made headlines after saying President Trump should win the Nobel Peace Prize.
When asked who should win the prestigious award, Prof Kelly simply said "None of them", to applause from the audience.
"The North Koreans are not negotiating from a position of weakness, they're negotiating from a position of strength," he said. "They now have the ability to strike the US with an intercontinental ballistic missile.
"It's the arrogance of outsiders to suggest the North Koreans are debating talking to us because of either Trump putting pressure on the right or Moon's liberal engagement on the left.
"If there is one state that we know doesn't listen to international pressure, it's North Korea. It's highly unlikely North Korea are choosing to engage us now because of what we on the outside have done. They're doing this because they have this weapon, and now they're shopping around.
"They're not interested in peace. They're interested in concessions."
NORTH KOREA'S SHOCK WARNING TO US
Pyongyang took aim at the US overnight, criticising what it called "misleading" claims that Trump's policy of maximum political pressure and sanctions are what drove the North to the negotiating table.
The North's official news agency quoted a Foreign Ministry spokesman warning the claims are a "dangerous attempt" to ruin a budding détente on the Korean Peninsula after Kim's summit late last month with Moon.
"The US is deliberately provoking the DPRK (North Korea) at the time when the situation on the Korean Peninsula is moving toward peace and reconciliation," the spokesman was quoted as saying.
North Korea also warned Washington that claiming Pyongyang was forced into talks by US pressure risked returning the peninsula "back to square one".
Last week, alarm bells sounded over a New York Times report claiming Trump would offer to remove US troops from South Korea during the summit.
But the leader refuted these claims.
"No, no no," he told reporters on Friday, although he did note that "at some point in the future, I'd like to save the money".
The exact date and location of the meeting are yet to be announced.
