A major international crisis is “much more likely” in Donald Trump’s second term, given the president-elect’s “inability to focus” on foreign policy, a former US ambassador to the United Nations has warned, according to the Guardian.

John Bolton, who at 17 months was Trump’s longest-serving national security adviser, was sharply criticized for his lack of knowledge, interest in the facts or coherent strategy. He described Trump’s decision-making as driven by personal relationships rather than a deep understanding of the national interest.

Bolton also rejected Trump’s claims during this year’s election campaign that he alone could prevent a third world war while bringing a swift end to the conflicts in Gaza and Ukraine.

“It’s typical Trump: it’s all bragging,” Bolton told the Guardian. “The world is more dangerous than when he was president. The only real crisis we had was the coronavirus, which was a long-term crisis and not against a specific foreign power.”

“But the risk of a 19th-century-style international crisis is much more likely in a second Trump term. Given Trump’s inability to focus on coherent decision-making, I am very concerned,” he added.

Bolton, 76, supported the 2003 invasion of Iraq and has called for US military action against Iran, North Korea and other countries for their efforts to build or procure nuclear, chemical or biological weapons.

Bolton was Trump’s national security adviser from April 2018 to September 2019.

Bolton also stated: “What I believed was that, like every American president before him, the weight of responsibility, certainly in national security, the seriousness of the issues he faced, the consequences of his decisions, would discipline his thinking in a way which would produce serious results. Turns out I was wrong. By the time I came to this conclusion many patterns of behavior had already been formed that never changed and it might well be that even if I had been there earlier I would not have been able to influence the situation. But it was clear very soon after I got there that intellectual discipline was not Trump’s.”

In a departure from traditional US foreign policy, Trump campaigned on the slogan “America First”, advocating isolationism, non-intervention and trade protectionism, including significant tariffs.

Bolton agreed with “many” of Trump’s decisions during his first term, but found they had the consistency of “a series of flashes.” “He has no philosophy, he does not practice politics as we understand it, he has no national security strategy. I mentioned in my book that his decisions are like an archipelago of dots. You can try to draw lines between them, but he can’t draw lines between them either. You try and gradually make one right decision after another. At least that’s what his advisers thought: that we could link several decisions together. But that wasn’t the way he saw it himself.”

The 45th president “can be charming,” Bolton conceded, and emphasized personal relationships with authoritarian leaders such as China’s Xi Jinping, North Korea’s Kim Jong Un and Russia’s Vladimir Putin. But he lacks the skills required for the position and has shown a blatant disregard for the national security briefing that presidents receive every day.

“He doesn’t know much about foreign policy. He doesn’t read much. He reads newspapers here and there, but he hardly ever reads news papers, because he does not consider them important. He doesn’t think these events are important. He thinks he’s looking the other person across the table in the eye and they’re making a deal and that’s the important thing,” he noted.

Trump believes he has a friendship with Putin, Bolton added. “I don’t know what Putin thinks his relationship with Trump is, but he thinks he knows how to play Trump, that Trump is an easy target. Trump doesn’t see that at all, he noted.

Trump has repeatedly praised authoritarian leaders such as Putin and Hungary’s Viktor Orban and has not ruled out pulling out of NATO. Asked about Trump’s now-infamous friendship with powerful men, the former national security adviser replied: “I guess a psychiatrist could understand that better.”

In recent days, Trump has again unsettled diplomats by threatening to take back the Panama Canal, asking the US to buy Greenland and proposing that Canada become the 51st state. Kim Darroch, who was Britain’s ambassador to Washington for four years from 2016, told Sky News that Trump’s second term would be “like an endless bar fight”.

Bolton agrees that his second term could be even more alienating and disruptive than his first: “He now feels more confident in his judgment, having been re-elected, which will make it even more difficult to have any kind of intellectual discipline in the decision-making”.