President Trump said his summit with North Korean leader Kim Jong Un wouldn’t have happened without Otto Warmbier, noting the American university student who was imprisoned by the regime “did not die in vain.”

“Otto Warmbier is a very special person and he will be for a long time in my life. His parents are good friends of mine,” Trump said during a Tuesday press conference after his meeting with Kim in Singapore. “I think without Otto, this would not have happened.”

Calling Warmbier’s death “terrible” and “brutal,” Trump said his experience forced people to “focus on what was going on, including North Korea.”

“I really think that Otto is someone who did not die in vain. I told this to his parents. Special young man and special parents,” Trump said. “He had a lot to do with us being here today.”

Warmbier, 22, died just days after returning to his Ohio home in a coma following his release by North Korea in June 2017.

The University of Virginia student was arrested in January 2016 for stealing a propaganda poster from a hotel and was sentenced to 15 years of hard labor.

Trump said he raised the issue of human rights with Kim, who has been called one of the worst human rights violators in the world by the United Nations for the brutal oppression of his people, including summary executions and jailing of political enemies.

“I believe it is a rough situation over there. No question about it. We did discuss it today strongly,” Trump said during the more than hour-long briefing, without offering any specifics. “Knowing what the main purpose of what we are doing is denuking.”

Asked about the thousands of North Koreans who are being held in the regime’s network of gulags in isolation with no knowledge of his summit with Kim, Trump said he believes his efforts to disarm the country will eventually help them.

“I think I helped them. There is nothing I can say. All I can do is do what I can do. We have to stop the nukes,” Trump said. “Not much I can do right now. At a certain point, I believe he is going to do things about it. I think they are one of the great winners today.”

The president also said he would not ease up on the punishing sanctions the US has imposed on North Korea until there is “significant improvement” in Kim’s treatment of his citizens.

“I want to start that process. Although you cannot finish that process for a while, but you cannot go back. Once we reach that point, I’ll give that serious thought,” he said.