President Donald Trump's claim that North Korean dictator Kim Jong Un had no knowledge of the horrific treatment American student Otto Warmbier endured while detained in his country is "inconceivable," a former United States ambassador to the United Nations said Thursday.

"It is totally impossible," former Gov. Bill Richardson, D-N.M., who served as ambassador in the Clinton administration, told MSNBC. "It is inconceivable that such a high-profile American prisoner like Otto Warmbier, that Kim Jong Un would not know."

Trump was slammed by politicians on both sides of the aisle after absolving Kim of blame in the death of Warmbier, 22, who died days after returning to the U.S. following 17 months of detention in North Korea.

Following a summit with Kim, Trump said at a press conference in Hanoi, Vietnam, that it "just wasn’t to [Kim's] advantage to let that happen." He added: "He tells me that he didn’t know about it, and I will take him at his word."

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That was a sharp reversal from last year's State of the Union address, just months after Warmbier's death, where Trump welcomed the American college student's tearful parents as his guests, telling them mid-speech, "you are powerful witnesses to a menace that threatens our world, and your strength inspires us all.”

Experts say it is unlikely Kim would not have known about a prized American in his country's custody. They said it was possible that he did not know exactly how Warmbier was being treated, and that Warmbier — who was sentenced to hard labor in North Korea after stealing a propaganda poster — had been accidentally roughed up more than he was supposed to be by his handlers.

"Given the North Korean leadership structure, it is possible that low-level guys could have done something to him, and they were afraid to send the information up" to Kim, according to Victor Cha, a government professor at Georgetown University and an MSNBC contributor. But, he added, "if he says he didn’t know about it, that should make it that much easier to apologize."

This is hardly the first time that Trump has expressed sympathy for world leaders accused of brutality. He also refused to condemn Saudi Crown Prince Mohammed bin Salman for the death of Washington Post columnist Jamal Khashoggi at a Saudi Arabian consulate in Turkey, despite CIA intelligence indicating the prince ordered the journalist's killing.

Trump also repeatedly showers accolades on Russian President Vladimir Putin, despite the Russian government's long list of abuses.

"It goes to the larger pattern of praise of Trump for the most brutal leaders on Earth."

"It goes to the larger pattern of praise of Trump for the most brutal leaders on Earth," said Michael Green, senior vice president for Asia at the Center for Strategic and International Studies and an Asia adviser under former President George W. Bush.

As for Kim, Green said, while there is a chance he may not have directly ordered Warmbier's death, he is behind some of the most "shocking torture and brutality" in his country's history, and Trump should not give him a pass.

"It’s possible he didn’t order it and didn’t know about it," he said. "On the other hand, that’s kind of irrelevant, because the system he’s presided over and made more brutal does that kind of thing."

Richardson, who was nominated for the Nobel Peace Prize for his diplomatic efforts with North Korea, said others in the North Korean regime were not aware of how horribly Warmbier had been abused. But he scoffed at the idea that Kim did not know.

"What’s interesting is the foreign ministry officials that we were negotiating with in North Korea to get Otto back, they told us that they did not know he was in that very, very vegetative state, that horrendous state that he was in," Richardson said.

"But the intelligence community is the ones that were apprehending and kept Otto Warmbier in custody. So for them not to have told the leader of the country in such a high-profile case is totally inconceivable."