U.S. President Donald Trump on Tuesday hailed North Korean leader Kim Jong Un's "courage" in taking steps toward denuclearization, but said that sanctions will remain in place until Pyongyang dismantles its nuclear weapons program.

In his second speech at the U.N. General Assembly, Trump highlighted his recent engagement with North Korea -- including a historic meeting with leader Kim in June in Singapore -- in a bid to replace "the specter of conflict with a bold and new push for peace."

"I would like to thank Chairman Kim for his courage and for the steps he has taken, though much work remains to be done," he said, referring to Kim by his title as chairman of the Workers' Party of Korea. "The sanctions will stay in place until denuclearization occurs."

(Getty/Kyodo)

The speech provided a stark contrast to Trump's maiden speech at the global body last year in which he threatened to "totally destroy" North Korea and called Kim a "rocket man" on a "suicide mission for himself and for his regime" with its "reckless pursuit" of nuclear weapons and ballistic missiles.

A year later, however, Trump has described the relationship with Kim as "very good" and even "extraordinary," as the United States aims to achieve the final, fully verified denuclearization of North Korea by the end of the president's first term in January 2021.

Trump is planning to hold a second summit with Kim "in the not too distant future" following the first-ever U.S.-North Korea summit at which Kim committed to "complete" denuclearization of the Korean Peninsula.

In an interview with Fox News on Tuesday, South Korean President Moon Jae In -- who discussed the possible timing and location of a second U.S.-North Korea summit during a meeting with Trump on Monday in New York -- said Trump could meet Kim before the end of the year.

In the U.N. address, Trump thanked Moon, Japanese Prime Minister Shinzo Abe and Chinese President Xi Jinping for their cooperation over the North Korean nuclear issue.

Nonetheless, Trump also condemned China over its "unfair" trade practices, as well as its massive and chronic trade surpluses with the United States.

"I have great respect and affection for my friend President Xi. But I have made clear our trade imbalance is just not acceptable," he said. "China's market distortions and the way they deal cannot be tolerated."

On Monday, the Trump administration invoked tariffs on an additional $200 billion in Chinese imports in response to Beijing's alleged intellectual property and technology theft.

The action was the most significant escalation yet in the trade war between the world's two largest economies. China immediately hit back, slapping additional tariffs on $60 billion in U.S. imports.

"The United States will not be taken advantage of any longer," Trump said Tuesday. "We will not allow our workers to be victimized, our companies to be cheated and our wealth to be plundered and transferred."

Unlike his conciliatory tone toward North Korea, the U.S. leader slammed Iran over its nuclear program and support for militant groups in the Middle East, urging all nations to isolate the regime in Tehran as long as its "aggression" continues.

Washington is cooperating with Japan and other countries that import Iranian oil to "cut their purchases substantially" so as to dry up the regime's revenues, according to Trump.

Trump defended the U.S. withdrawal from the 2015 nuclear agreement between Iran and world powers and the U.S. reimposition of sanctions on Tehran, saying, "The Iran deal was a windfall for Iran's leaders."

"The dictatorship used the funds to build nuclear-capable missiles, increase internal repression, finance terrorism, and fund havoc and slaughter in Syria and Yemen," he said.

"We cannot allow the world's leading sponsor of terrorism to possess the planet's most dangerous weapons."