Donald Trump has a few roadblocks in the way of achieving peace on the Korean peninsula.

One is North Korea's determination not to give up their nuclear weapons, for fear of the authoritarian regime losing the best protection they have.

Another is his lack of preparation, and the fact that on an issue so sensitive, his "Art of the Deal" skills seem to be coming up short.

But the third problem at the very back of his mind is the most morally problematic: North Korea's decades-long history of brutality and human rights abuses.

The closed-minded self-interest Americans are so often derided for allows Mr Trump to put the incredible suffering the Kim regime has put upon its own people to one side, but the story of Otto Warmbier has proven harder to ignore.

Otto Warmbier was jailed in North Korea in December 2015. He died two years later. ( Reuters: Kyodo, file )

Otto Warmbier was a gifted 21-year-old University of Virginia student with a fondness for adventure.

In December 2015 he took a risk, and booked a tour of North Korea for Christmas.

The North Korean regime alleged that while on tour, Mr Warmbier removed a propaganda poster from the wall of his hotel.

For this, he was detained, forced to read a ridiculous confession while fighting back tears, and sentenced to 15 years' hard labour.

In mid-2017, after 17 months in North Korean detention, Mr Warmbier was returned to his family in Ohio in a coma.

His parents said he showed signs of having been physically tortured, though that has been disputed by a coroner.

He never regained consciousness after returning to America. He died days after his arrival.

He invited the Warmbier family to the 2018 State of the Union, and addressed them directly, saying "You are powerful witnesses to a menace that threatens our world, and your strength inspires us all."

"Tonight, we pledge to honour Otto's memory with American resolve."

But in the months afterwards, he rapidly changed tack … talking instead of a growing relationship with Kim Jong-un following the 2018 Winter Olympic Games in South Korea.

On Thursday, despite the collapse of denuclearisation talks in Hanoi, Vietnam, Mr Trump absolved Mr Kim of responsibility for Otto's death.

"I really believe something horrible happened to him, and I really don't think the top leadership knew about it," Mr Trump told reporters.

"Those prisons are rough, they're rough places and bad things happened.

"He (Mr Kim) felt badly about it. He knew the case very well, but he knew it later. And you've got a lot of people, big country, a lot of people.

"He tells me that he didn't know about it, and I will take him at his word. Go ahead in the back. No, in the back behind you. Thank you."

Otto's parents, Fred and Cindy Warmbier, filed a wrongful death suit against North Korea. ( AP: Frank Franklin II )

At home, these comments have been rubbished by Republicans and Democrats alike.

"He gave cover, as you said, to a leader who knew very well what was going on with Otto Warmbier," Trump-ally and former Republican senator Rick Santorum told CNN.

Republican Senator Lindsey Graham said he didn't "buy it for a second" that Mr Kim could be unaware of what was happening to Mr Warmbier.

Former UN ambassador Bill Richardson, an expert in returning American hostages from hostile states, went further, saying it was "inconceivable" that Mr Kim would not have been briefed.

Mr Richardson, who was nominated for a Nobel Peace Prize earlier this year for his work on North Korea, added that Mr Warmbier was "the biggest bargaining chip that North Korea had with the US".

Otto Warmbier never regained consciousness after returning to the US. ( AP: The Cincinnati Enquirer )

"It's not right. And the President should know better," he said.

This is the third time in the last year that Mr Trump has sided with an authoritarian leader over the findings of his own government and intelligence agencies.

In June last year, he sided with Russian President Vladimir Putin over his own intelligence agencies on the issue of Russia's state-sponsored meddling in the 2016 US Presidential election.

"I don't see any reason why it would be" Russia, Mr Trump said. "President Putin was extremely strong and powerful in his denial today."

Mr Trump and Mr Putin are mutual admirers. ( AP: Pablo Martinez Monsivais )

In October last year, Mr Trump accepted the word of King Salman of Saudi Arabia, who gave the President a "flat denial" that the Saudi Crown Prince had ordered the killing of Washington Post journalist Jamal Khashoggi in his country's consulate in Istanbul.

The three situations are similar in many ways, though there is one important difference.

The President has been clear that his incentive to get along with North Korea is denuclearisation, and blaming Mr Kim for Otto Warmbier's death would provide a roadblock to that goal.

In Saudi Arabia's case, Mr Trump says he is committed to securing billions of US dollars in arms deals with the Kingdom, and doesn't want to unnecessarily jeopardise that investment opportunity.

But with Russia, the advantages the US would gain by accepting Mr Putin's word are more unclear.

Donald Trump has sided with Saudi leader Mohammed bin Salman in order to protect arms deals. ( Reuters: Kevin Lamarque )

In the absence of a clear national interest in appeasing Mr Putin, analysts are left to wonder if Mr Trump's interest is more personal.

Mr Putin has at various times been personally praising of Mr Trump as a leader, and has absolved him of failure by blaming what he perceives as America's shortcomings on a "deep state" apparatus of bureaucrats working to undermine Mr Trump.

Whether Mr Trump has reasons to take Mr Putin's side other than a desire to respond in kind to the Russian President's compliments is the subject of investigation by congressional committees, law enforcement agencies and Special Counsel Robert Mueller.

They are probing President Trump's finances and contacts to see if he has something personally to gain by taking Mr Putin's side over his own government agencies.