In blunt terms, Trump warned the US would "totally destroy North Korea" if forced to defend itself or its allies. He said while the US has "great strength and patience," its options could soon run out.
Directly putting the country's leader on notice, Trump suggested Kim Jong Un could not survive an American attack.
"Rocket Man is on a suicide mission for himself," he said.
It was a characteristically bombastic approach to a crisis that's growing in scale. Throughout his address -- the most closely watched foreign policy remarks of his presidency -- Trump brought frank assessments to a range of sticky global flashpoints.
He declared the Iran nuclear deal all but dead, saying it was an "embarrassment" to the United States. He bluntly described some regions of the world as "going to hell." And he revived his use of the term "radical Islamic terrorism," vowing to stamp out terrorists worldwide.
But it was Trump's remarks about North Korea that prompted the loudest buzz in the soaring, green-hued General Assembly hall, where Trump spoke to more than 100 world leaders and diplomats.
"It is an outrage that some nations would not only trade with such a nation but would arm, supply and financially support a country that imperils the world," he said.
He warned nations against becoming "bystanders to history" and thanked members of the UN Security Council -- where he's secured key victories through passage of sanctions measures against North Korea -- for escalating their rebukes of Pyongyang.
He directed similar ire toward Iran, which he accused of supporting terrorists and destabilizing the region.
"The Iranian government masks a corrupt dictatorship behind the false guise of a democracy," Trump said. "It has turned a wealthy country with a rich history and culture into an economically depleted rogue state whose chief exports are violence, bloodshed and chaos."
He left little doubt to his plans for the nuclear deal, which was brokered under the Obama administration and lifted some sanctions on the country in exchange for curbing aspects of its nuclear program.
"The Iran deal was one of the worst and most one-sided transactions," Trump said. "That deal is embarrassment to the US and I don't think you've heard the last of it, believe me."
Trump faces a mid-October deadline for re-certifying Iran's compliance with the agreement. US officials say Trump is still weighing his next moves and plans to announce his intentions next month.
He also lambasted Venezuela's leader Nicolas Maduro, accusing him of depriving his people in the same of socialist ideas. "The Venezuelan people are starving and their country is collapsing," Trump said.
Trump has delivered major foreign policy addresses before, but the issues at the United Nations are broader and the geographic spread of Trump's audience wider. The message he delivered here will resonate in capitals worldwide, where officials and leaders are still seeking a cohesive foreign policy doctrine from new American leader.
In his remarks, Trump sought to encapsulate his worldview through the theme of "sovereignty," suggesting that nations acting in their own self-interest would create a more stable world.
"As President of the United States, I will always put America first, just like you, as the leaders of your countries, will always and should always put your countries first," he said to scattered applause. "All responsible leaders have an obligation to serve their own citizens, and the nation-state remains the best vehicle for elevating the human condition."
Trump told world leaders that he would not insist their countries adopt US values.
"In America, we do not seek to impose our way of life on anyone, but rather to let it shine as an example for everyone to watch," Trump said.
For a President whose election and elevation to the White House was among the most improbable in modern political history, the United Nations stage represented a milestone, even if some in the audience still find the sight of Trump in front of the iconic green marble jarring
. Trump's three eldest children -- Donald Jr, Ivanka and Eric Trump -- all attended his speech, along with first lady Melania Trump.
Trump's remarks, which ran 41 minutes long, were written with the help of Stephen Miller, Trump's senior policy adviser who also acts as the presidential speechwriter. Miller's nationalist worldview was evident throughout, from Trump's critiques of free trade agreements to his insistence that refugees are better resettled in their own regions than in the United States. In a return to a campaign-style phrase, Trump declared that America's middle-class would be "forgotten no more."
So, too, was Miller's voice evident in Trump's use of the phrase "radical Islamic terror," a loaded term that some argue unfairly impugns an entire religion. Trump, who employed the term frequently on the campaign trail, curtailed its use as President. But he returned to the description on Tuesday, claiming his administration had done more to go after groups like ISIS than his predecessor.
"Our military will soon be the strongest it's ever been," he said.
Trump has demeaned the United Nations in the past, claiming the body is ridden with bureaucracy and overspending. His first remarks as president here on Monday were centered on reforming the institution's practices.
During his address, however, Trump was optimistic about the UN's ability to improve global security through collective action.
"Major portions of the world are in conflict, and some in fact are going to hell, but the powerful people in this room, under the guidance and auspices of the United Nations, can solve many of these vicious and complex problems," he said.
In his remarks, Trump made no mention of climate change, an issue the United Nations has worked to combat through the Paris accord, an agreement Trump has lambasted. He also made few references to Russia, whose actions in Ukraine have caused deep anxiety throughout Europe.
Among the hundreds of diplomats assembled to watch his speech, reaction was largely muted. He received applause for declaring that countries should act in their own interest and for his backing of women's equality, but only bemused murmurs for his bellicose threats toward North Korea.