Donald Trump threatened to “totally destroy” North Korea if Kim Jong-un refuses to back down from his nuclear missile program, in a debut speech to the United Nations that painted a dark picture of a world under siege and ratcheted up international tensions.

The U.S. President took a hard line in his first address to the UN General Assembly Tuesday, warning he might tear up the Iran nuclear deal, blaming migrants for hurting the American working class, slamming socialism for destroying Venezuela and vowing to “crush loser terrorists.”

The packed room was largely silent during a speech that was a far cry from the usual cautious language of the United Nations, offering occasional muted applause, while some diplomats folded their arms and wore grim expressions.

Mr. Trump used his 40-minute turn before the world’s leaders to lay out an international version of his “America first” ideology, insisting all countries embrace a “reawakening” of patriotism but come together to meet international threats. The speech comes as the President faces tumult at home, with few domestic policy achievements and a series of investigations into his campaign’s connections to Russian interference in last year’s elections.

The address was silent on a number of major international problems, including climate change and the attacks on Rohingya people by the military of Myanmar.

There were echoes between Mr. Trump’s rhetoric Tuesday and his combative inaugural address, which described the “American carnage” of shuttered factories that the President vowed to reverse by embracing a tough new nationalism.

“Major portions of the world are in conflict and some in fact are going to hell,” he said at the UN, drawing whispers among the assembled leaders.

No international issue has confounded the Trump administration like North Korea’s nuclear and missile program. In the past month, Mr. Kim has fired two missiles over Japan and conducted his country’s most powerful test of a nuclear weapon. Mr. Trump has responded by mocking him on Twitter with an epithet derived from an Elton John song.

“Rocket Man is on a suicide mission for himself and for his regime,” Mr. Trump warned Tuesday, saying that the United States doesn’t want war in North Korea but that if “forced to defend itself or its allies, we will have no choice but to totally destroy North Korea.”

Mr. Trump’s plan appears to be to make Mr. Kim back down under threat of retaliation, but it is certain to heighten fears the world is moving closer to a nuclear confrontation. Such a war would be a humanitarian catastrophe that could put at risk tens of millions of people on the Korean Peninsula and in Japan. North Korea’s ambassador to the UN, Ja Song-nam, walked out before the speech.

Carla Anne Robbins, national-security expert at the Council on Foreign Relations in Washington, said that beyond goading Mr. Kim, the President’s comments didn’t seem to lay out a strategy for solving the problem.

“I did not see much of a way forward here, other than reiterating what the ultimate goal is and threatening [North Korea] with total obliteration,” she said at a roundtable with reporters after Mr. Trump’s address. “The impact of all of this was to crank Pyongyang up and not offer a huge amount of reassurance to the allies.”

Prime Minister Justin Trudeau, speaking in Ottawa before heading to the UN, called for diplomacy.

“I share everyone’s concern about the reckless behaviour by the North Korean regime and continue to believe that working with partners and allies in the region and around the world, including China, Japan, South Korea and the United States, is the best way to de-escalate this situation,” he said.

Later on Tuesday, at an awards gala in New York, Mr. Trudeau called on world leaders to renew their commitment to global alliances such as NATO and multilateral bodies such as the United Nations.

Mr. Trudeau will address the UN General Assembly later this week. His push for global co-operation comes on the heels of the speech by Mr. Trump, who encouraged other world leaders to put their countries first.

Israeli Prime Minister Benjamin Netanyahu, however, unequivocally praised Mr. Trump. “In over 30 years in my experience with the UN, I never heard a bolder or more courageous speech,” he tweeted.

Mr. Trump bashed the 2015 agreement that saw Iran halt its development of nuclear weapons in exchange for the United States and other countries lifting economic sanctions.

“The Iran deal was one of the worst and most one-sided transactions the United States has ever entered into. Frankly, that deal is an embarrassment to the United States and I don’t think you’ve heard the last of it – believe me,” he said.

He also trained his fire on Venezuela, where President Nicolas Maduro has seized dictatorial powers amid an economic crisis. Mr. Trump blamed Mr. Maduro’s socialism for the country’s problems, arguing that the ideology “has delivered anguish and devastation and failure” in any country that has adopted it.

Both Iran and Venezuela hit back. On Twitter, Iranian Foreign Minister Mohammad Javad Zarif described Mr. Trump’s address as an “ignorant hate speech” that “belongs in medieval times.” Mr. Maduro told a rally in Caracas that the U.S. President was “the new Hitler of international politics.”

Stewart Patrick, a foreign-policy adviser in the George W. Bush administration, said Mr. Trump’s overarching goal seemed to be reconciling his nationalistic campaign rhetoric with the imperative to co-operate on North Korea and other problems. In the speech, the President lauded the patriotism of other countries – including Poland, France and Britain – drawing a parallel with his own “America first” agenda.

“He managed to square a circle, if you will,” Mr. Patrick, author of The Sovereignty Wars, said at the Council on Foreign Relations roundtable. “He said ‘Look, we’re here to pursue our national interests but, of course, all of you countries and all of you leaders who are here are here to pursue your national interests.'”

The Globe and Mail, September 19, 2017