“Unless we keep the pressure on North Korea, they are not going to change, and I am very afraid that we are going to let up on this pressure,” she said at an event in Washington, D.C.
"This should not be a partisan issue. This is a problem. This is not only a nuclear problem, this is a problem that we're dealing with absolute evil," she added.
Cindy Warmbier responded to the recent revelation that North Korea gave the U.S. a $2 million bill for her son's medical expenses when senior diplomats arrived to bring Otto home - saying had she known they wanted money, she would have paid.
"I don't fault anyone for signing to get Otto home. In fact, I applaud Ambassador Yun for making sure he brought Otto home," she said. "If I had to, I would've raised the money, and I wish they would've asked for the money from day one."
In March, Cindy Warmbier and her husband Fred spoke out after President Donald Trump seemed to absolve Kim of knowing about or being responsible for Otto Warmbier’s treatment and eventual death. They have said that their son was "systematically tortured" by Kim's regime.
"Kim and his evil regime are responsible for the death of our son Otto. Kim and his evil regime are responsible for unimaginable cruelty and inhumanity. No excuses or lavish praise can change that," the parents said in a statement at the time.
On Friday, Cindy Warmbier said that while she supported Trump's effort to negotiate with Kim, she was not optimistic about diplomacy.
“There’s a charade going on right now -- it’s called diplomacy. How can you have diplomacy with someone who never tells the truth? That's what I want to know, I'm all for it, but I'm very skeptical," she said.
“He lies and he lies and he lies, all for himself,” she said of Kim, comparing him to Hitler, except that Kim is “doing it to all of his people.”
“North Korea is a cancer on this earth, and if we ignore this cancer, it’s not going away, and it's going to kill all of us,” she added.
As the family has before, Cindy Warmbier described the heart-rending scene of seeing her son for the first time in June 2017 when he was brought back to the U.S.
“My gorgeous boy -- who every girl had an immediate crush on -- looked like a monster,” she said.
“The look in his eyes -- which I didn’t know he was blind at the time -- was absolute horror, horror like he had seen the devil - and he had. He was with the devil,” she said.