Speaking at the Center for Strategic and International Studies in Washington, Bolton suggested that North Korean leaders were happy to see the former national security advisor ousted from his position earlier this month.
North Korea “has not made a strategic decision to give up nuclear weapons,” he said,
"The strategic decision that Kim Jong Un is operating through is that he will do whatever he can to keep a deliverable nuclear weapons capability and to develop and enhance it further."
“He may try to get relief from international sanctions. He may make some concessions. But under current circumstances, he will never give up the nuclear weapons voluntarily.”
Though Bolton didn't mention Trump by name, his views were contrary to the president's strategy in trying to broker a nuclear deal with the rogue state. Trump and North Korean leader Kim Jong Un have repeatedly, with Trump claiming each meeting a success and talking up his relationship with Kim.
Trump said he fired Bolton earlier this month over policy disagreements and clashes with other administration officials. Trump said Bolton's views had set the U.S. back "very badly" in talks. For his part, Bolton said he first offered to resign.
Upon Bolton's abrupt departure from the White House, Trump blasted his former national security adviser's "Libya model," which saw that country give up its nuclear weapons in 2003 in exchange for the lifting of economic sanctions. Libyan leader Muammar Qaddafi was eventually toppled and died in 2011.
“It may be the Libya model is not possible,” Bolton said. “But what I regard as even worse, in a way, is pretending that you’re getting to a resolution of the nuclear issue when you simply allow North Korea still to have a nuclear capability but give it enough economic assistance … that gives the regime a lifeline it currently doesn’t have.”
North Korean officials expressed anger at Bolton's Libya comments, with many in North Korea arguing that nuclear weapons are essential for survival.
Talks between American and North Korean officials have stalled since Trump and Kim walked away from their second summit in February. Kim wanted sanctions relief in exchange for partial disarmament.
In the several months since, North Korea has run several short-range missile tests. Trump has largely downplayed the tests, saying they haven't violated any agreements.
On Monday, Bolton said American officials should focus on taking a tougher approach with North Korea, not "can we get another summit with Kim Jong Un, or what the state of staff-level negotiations are to achieve a commitment from North Korea it will never honor."
During his speech, Bolton said the U.S. should think about a possible regime change and working with China toward the reunification of the two Koreas.
"If you believe ... that it is unacceptable for North Korea to have nuclear weapons, at some point military force has to be an option," he said.
Bolton is well known for his hawkish stance on foreign policy and is an advocate for U.S. intervention abroad against Washington's adversaries.
At the start of his speech, he alluded to North Korea's dislike of his views.
"I'm also sure that the leadership of North Korea is delighted that I'm here today in a private capacity," he said.
The Associated Press contributed to this report.