WASHINGTON — In his first public comments since leaving the White House, John R. Bolton, the former national security adviser, delivered a stark warning Monday about President Trump’s approach to North Korea, undercutting the president’s yearslong insistence that North Korea wanted to make a denuclearization deal with him.
Without mentioning Mr. Trump by name, Mr. Bolton, a longtime critic of the North Korean regime, made it clear he thought the president’s courtship approach to diplomacy with Kim Jong-un, the North Korean leader, was only increasing North Korea’s power. And while Mr. Trump has made a deal with North Korea one of his signature foreign policy goals, Mr. Bolton asserted that there had been no gains under this charm offensive approach.
“The strategic decision 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,” Mr. Bolton said Monday during a speech in Washington. “Under current circumstances, he will never give up the nuclear weapons voluntarily.”
Mr. Bolton was ousted from the Trump administration less than a month ago amid disputes over how to handle major foreign policy challenges, including North Korea.
Stopping nuclear proliferation in the Korean Peninsula is where the United States needs “to focus our attention,” Mr. Bolton said, “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.”
For Mr. Trump, the showy summits have been among his signature foreign policy achievements, held up as historic firsts. But there has been no sign that North Korea’s nuclear provocations have diminished since Mr. Trump’s outreach and the exchange of “beautiful” letters he likes to show off.
When pressed about whether Mr. Bolton thought Mr. Trump’s efforts to befriend and charm Mr. Kim would work, Mr. Bolton deferred. “I’m not going to comment on that,” he said. “Nice try.”
Mr. Bolton also directly opposed Mr. Trump’s position that the United States was in “no rush” for North Korea to give up its nuclear weapons. “Time works against those who oppose nuclear proliferation,” Mr. Bolton said. “A relaxed attitude to time is a benefit to the likes of North Korea and Iran.”
Mr. Trump and Mr. Bolton clashed on North Korea policy even before Mr. Bolton left the administration. During a four-day state visit to Japan in May, Mr. Trump contradicted Mr. Bolton and Shinzo Abe, the Japanese prime minister, who both called North Korea’s short-range ballistic missile tests a violation of United Nations Security Council resolutions.
“North Korea fired off some small weapons, which disturbed some of my people, and others, but not me,” Mr. Trump wrote on Twitter, noting that he trusted Mr. Kim to “keep his promise to me.”
Mr. Trump has also cited Mr. Bolton’s comments about using a “Libyan model” for disarmament in North Korea as among the reasons for his dismissal, and noted that he blamed Mr. Bolton more than Mr. Kim for the stalled talks. “He wanted nothing to do with John Bolton,” Mr. Trump told reporters this month, of Mr. Kim.
But Mr. Bolton’s comments on Monday revealed more about the deep disagreements on North Korean strategy that were at play within the Trump administration, and raised questions about what other splits with Mr. Trump he may speak about publicly.
Mr. Bolton made his comments during a speech at the Center for Strategic and International Studies in Washington, where he was not pressed during a question-and-answer session on any topics other than the Korean Peninsula and America’s stance toward Asia.
His appearance, where Mr. Bolton said he was glad to “speak unvarnished about the threat posed by North Korea,” was greeted with some expectation that he might also shed light on the whistle-blower complaint that has prompted an impeachment inquiry.
Mr. Bolton was still the national security adviser on July 25, the day Mr. Trump spoke on the phone with Volodymyr Zelensky, the president of Ukraine, and repeatedly pressured Ukraine’s leader to investigate Joseph R. Biden, Jr., the former vice president and a political rival.
It is typical for the national security adviser to be on all calls with foreign leaders, but Mr. Bolton has not said whether or not he was listening in on the call, which has become the major flash point in a battle over impeachment between Mr. Trump and House Democrats.
Instead, he stuck to dire warnings on North Korea.
“Every day that goes by makes North Korea a more dangerous country,” he said. “When does it become too late? Today is better than tomorrow. Tomorrow is better than the next day.”