WASHINGTON — Former national security adviser John Bolton made clear on Monday in his first public remarks since his contentious departure from the White House that he opposed President Donald Trump’s approach to North Korea and Iran as multiple current and former administration officials say he also was at odds with his former boss over a July phone call with the president of Ukraine.

Three officials said Bolton argued against Trump calling Ukrainian President Volodymyr Zelenskiy on July 25 because he was concerned the president wasn’t coordinating with advisers on what to say and might air personal grievances. The officials declined to say whether that included concerns that Trump might raise questions about his political rival, former Vice President Joe Biden, and Ukraine.

Bolton was among the senior members of the president’s national security team, including Vice President Mike Pence, who did not listen in on the Zelenskiy call, officials said.

Now there are growing fears among people close to Trump that Bolton and his allies are poised to inflict the most damage on the president given his unceremonious exit from the White House and how much he knows from his 17 months there.

“They know where a lot of the bodies are buried,” one person close to the White House said.

During his appearance Monday at a forum on U.S.-Korea policy, Bolton did not mention Ukraine controversy or House Democrats’ impeachment inquiry that’s underway because of it.

But he showed a willingness to criticize the president that other top national security officials who’ve left the administration have largely avoided. And when the moderator of the event suggested Bolton was restricted on talking about his time in the Trump administration, Bolton interjected to make clear that any such restriction is “self-imposed.”

He began his remarks by noting his new freedom to speak in “unvarnished terms.” For the next 45 minutes he argued — without ever mentioning Trump by name — that the president’s approach to North Korea and Iran are largely wrongheaded.

His disagreement with Trump over calling Zelenskiy and delaying lethal military aid to Ukraine shows the clashes between the two of them on foreign policy challenges touched at least three continents.

By July, when Bolton was arguing against Trump calling Zelenskiy, his influence on the president had weakened amid growing tensions over policies like Iran and North Korea.

“He was already cut out of the process so his opinion didn’t matter," one official said of Bolton.

While they weren’t on the Zelenskiy phone call, typically such senior officials as the national security adviser and vice president would later be read in on the contents of the discussion with a world leader if they weren’t listening in real time.

Bolton declined to comment.

A White House official confirmed Pence was not on the call.

Bolton left the White House two weeks before the White House publicly released notes from the call and a whistleblower complaint alleging Trump sought help from Zelenskiy to investigate a political rival.

He used his public appearance on Monday to detail a broader criticism of Trump’s approach to the national security challenges facing the world today.

“It’s a time for more U.S. involvement and leadership,” he said. “More, and not less.”

On North Korea, Bolton said North Korean leader Kim Jong Un has no intention of giving up his nuclear weapons — which Trump has insisted he will as part of their one-on-one negotiations. Bolton also argued that “at some point military force has to be an option.”

“Under current circumstances he will never give up the nuclear weapons voluntarily,” he said during an appearance at a forum on U.S.-Korea policy at the Washington-based think tank Center for Strategic International Studies.

Asked later if “bromance” diplomacy is the best approach, he smiled and said “no comment.”

He was critical of dismissing North Korea’s recent missile tests as insignificant, as Trump has, saying it sends the message to other countries that it’s permissible to violate sanctions.

“When you ask for consistent behavior from others, you have to demonstrate it yourselves,” Bolton said. “And when you fail to do that, we open ourselves and our policy up to failure.”

He also criticized the idea of cutting a smaller North Korea deal that lifts some sanctions in exchange for Pyongyang shutting down part of its nuclear program, saying such a deal would only benefit the Kim regime.

“Yet there’s a world out there that’s ready to fall sucker to that kind of argument,” he said.