John Bolton spoke Monday in his first big public appearance since his acrimonious split with President Trump three weeks ago.

And while Bolton didn’t weigh in on the growing Ukraine scandal, he did rebuke the Trump administration over one of its central foreign policy initiatives: the pursuit of a nuclear deal with North Korean leader Kim Jong Un.

Appearing at the Center for Strategic and International Studies, Bolton declined to directly address things that had occurred during his time in the White House. But he made few bones about his concerns surrounding Trump’s continued pursuit of the elusive deal.

Bolton set the tone by noting early on that he was about to speak about North Korea in “unvarnished terms” and suggested that Kim was happy to see him outside the White House. Bolton then suggested that the negotiations between the two sides were very likely to be fruitless.

“I don’t think the North Koreans will ever voluntarily give up enough” in negotiations, Bolton said, adding, “There is no basis to trust any promise that regime makes.”

Bolton said the United States should stop focusing on summits with Kim and instead pursue a harder approach involving possible regime change and even military force to stop the North Korean nuclear program.

He also suggested that the Trump administration, as it pursues a nuclear deal, is giving North Korea too much of a pass on its violations of U.N. Security Council sanctions.

“North Korea today, as we speak, is violating” those sanctions, Bolton said. “When the U.S. led the fight to get those resolutions, and we say we really don’t care, other countries draw their own conclusion that they don’t really care about enforcing sanctions.

“When you ask for consistent behavior from others, you have to demonstrate it yourself.”

Bolton at other times demurred when asked to directly comment on internal administration matters. He was asked whether he agrees with the idea of “bromance diplomacy” — a term used to reflect Trump’s repeated efforts to emphasize how nice Kim is to him. Bolton said, “I’m not going to comment on that,” as the audience laughed. “Nice try.”

The idea that Bolton would take these positions is hardly surprising. He is among the more hawkish foreign policy voices in today’s Republican Party, and he took similar positions on North Korea long before joining the administration. But it was notable that he decided to raise ideas that were so contrary to Trump’s No. 1 foreign policy goal so soon after leaving the administration.

Bolton has been sending signals ever since his exit that he’s not particularly optimistic about what lies ahead in Trump’s foreign policy. Within hours of Bolton’s resignation announcement, an anonymous aide was telling reporters, “Since Ambassador Bolton has been national security adviser over the last 17 months, there have been no bad deals.” (The implication being that any deals that come now would not reflect upon Bolton.)

The big question with Bolton is how far he’s willing to go — and whether he might be a key witness in the Democrats’ impeachment inquiry over Ukraine. Bolton was in office when, according to a whistleblower, the White House attempted to bury what Trump told Ukraine’s president on a code-word-level National Security Council computer. As national security adviser, Bolton led that council.

When Bolton departed earlier this month, Trump attacked him for having advocated in 2018 the “Libya model” for North Korea — the idea that North Korea would completely abandon its nuclear program in exchange for sanctions relief.

“When he talked about the ‘Libyan model’ for Kim Jong Un, that was not a good statement to make,” Trump said, noting that the Libya model led to the downfall of longtime Libyan leader Moammar Gaddafi. “That was not a good statement to make. And it set us back.”

Bolton said Monday that the Libya model was “feasible” yet difficult. But he then contrasted it with the folly of seeking a middle-ground approach with North Korea.

“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.”