WASHINGTON - Former National Security Adviser John Bolton said military force has to remain an option in dealing with North Korea's nuclear weapons and missile programs because it will not follow through with its commitment to denuclearize and negotiate away its programs.

In his first public speech since his departure from the White House, Bolton told an audience Monday at the Center for Strategic and International Studies (CSIS), a Washington-based think tank, that North Korean leader Kim Jong Un will not "honor" his denuclearization commitment and give up the country's nuclear weapons and missile programs through diplomacy.

WATCH: Bolton comments on N. Korea weapons

Bolton's position appeared to contradict approaches that President Donald Trump has been taking toward North Korea. Before his first summit with Kim in June 2018, Trump said North Korea had "agreed to denuclearize."

Bolton said the questions to focus on now are 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" that Bolton thinks North Korea "will never honor."

John Bolton, left, and others attend an extended bilateral meeting between North Korea's leader Kim Jong Un and U.S. President Donald Trump, in Hanoi, Vietnam, Feb. 28, 2019.

He said the reason that North Korea will not follow through his denuclearization commitment is because the country "has not made strategic decision to give up its nuclear weapons."

"In fact, I think the contrary is true," he said. "I think 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."

Kim has made commitments to denuclearize through his New Year's Day speech given this year and through messages conveyed to Seoul and Beijing last year.

Bolton said Kim may offer to carry out partial denuclearization while he seeks for sanctions relief, but "under current circumstances, he will never give up the nuclear weapons voluntarily."

At the Hanoi Summit in February, Kim asked Trump to lift sanctions in exchange for dismantling a part of its nuclear weapons facilities, which Trump rejected, asking for full denuclearization instead before any sanctions relief.

FILE - U.S. President Donald Trump, left, conducts a meeting in the Oval Office of the White House in Washington, May 22, 2018, as then-National Security Adviser John Bolton, right, looks on.

In order to thwart growing dangers from North Korea's nuclear weapons program, Bolton said, "At some point, military force has to be an option."

Otherwise, Bolton sees North Korea becoming "the new A.Q. Khan, the Walmart or the Amazon of deliverable nuclear weapons," proliferating nuclear weapons and spreading threats around the world.

A.Q. Khan — Abdul Qadeer Khan, known as the father of Pakistan's nuclear program — confessed in 2004 he sold nuclear secrets to North Korea, Iran and Libya, proliferating nuclear weapons technology to those countries.

Bolton left his post as President Donald Trump's third national security adviser earlier in September, apparently due to clashes he had with Trump on how to handle foreign policy challenges, including North Korea's nuclear weapons program.

In April 2018, Bolton, a foreign policy hawk, called for applying a Libyan model to North Korea, which was criticized by Pyongyang. In the early 2000s, Libyan leader Moammar Gadhafi agreed to give up his nuclear weapons program in exchange for lifting sanctions. Shortly after renouncing his nuclear program, Gadhafi was overthrown and killed by rebels.

After Bolton's departure, Trump said Bolton made a mistake offending North Korea by demanding that it follows a Libyan model.

Trump has shown leniency toward North Korea's short-range missile tests conducted since May. Trump called the tests "very standard," and said that Kim kept his promise not to test intercontinental ballistic missiles (ICBM).

But Bolton said the recent North Korean tests violated the United Nations Security Council resolutions he helped to draft in 2006, which ban the country from launching a ballistic missile.

National security adviser John Bolton listens during a press briefing at the White House, Jan. 28, 2019, in Washington. (AP Photo/ Evan Vucci)

Unlike Trump, who has been downplaying North Korea's short-range missile launches this summer, Bolton underscored the dangers of those tests.

"The testing of shorter-range ballistic missiles that we've seen in recent months doesn't give us any reason to think that those are not threatening because the capabilities, the technology, things like maneuverability of close-range or short-range ballistic missiles, by definition can be adopted to the longer-range ballistic missiles," said Bolton. "So that indeed, the testing that's going on now is not unthreatening."

The reason North Korea has not launched ICBMs or nuclear weapons is because he believes the country has completed developing technologies to produce them and finds no need to test those technologies.

"One reason, one very good, very troubling reason why there's no more testing of nuclear weapons for the moment or of long-range missiles is that North Korea has in its judgment, for well or ill, finished testing and can produce nuclear warheads and long-range ballistic missiles," Bolton said. "That's not an encouraging sign. That's a sign to be worried about."

Also, unlike Trump, who said he is "not in a rush" to denuclearize North Korea, Bolton suggested the U.S. needs to take immediate actions to remove North Korea's nuclear weapons program, as the danger continues to grow.

"When the danger is perceptible, the costs of acting are low, the failure to act guarantees that the threat will grow, and the ultimate cost will be higher," Bolton said..

He continued, "Every day that goes by makes North Korea a more dangerous country. You don't like their behavior today? What do you think it'll be when they have nuclear weapons that can be delivered to American cities? ... Today is better than tomorrow. Tomorrow is better than the next day."