NEW YORK (CBSNewYork/AP) — President Donald Trump made his debut at the United Nations at a meeting calling for reforms at the organization as tensions continued to rise over North Korea.

In his first visit to the U.N. since taking office, the president is attending meetings Monday before addressing the General Assembly on Tuesday.

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Monday morning, Trump addressed a U.S.-sponsored event on reforming the 193-member organization he has sharply criticized in the past.

“The United Nations was founded on truly noble goals. These include affirming the dignity and worth of the human person and striving for international peace. The United Nations has helped advance toward these goals in so many ways: Feeding the hungry, providing disaster relief, and empowering women and girls in many societies all across the world. Yet in recent years the United Nations has not reached its full potential because of bureaucracy and mismanagement,” Trump said.

“We seek a United Nations that regains the trust of the people around the world,” Trump said. “To honor the people of our nations, we must insure that no one, and no member state, shoulders a disproportionate share of the burden, and that’s militarily or financially.”

He called on the U.N. to cut bureaucracy, reform outdated system and for member nations to look for ways to change “business as usual” and “champion truly bold reforms.”

As a candidate for president, Trump labeled the U.N. as weak and incompetent, and not a friend of either the United States or Israel. But he has softened his tone since taking office, telling ambassadors from U.N. Security Council member countries at a White House meeting this year that the U.N. has “tremendous potential.”

Trump and U.N. Secretary-General Antonio Guterres spoke at the meeting. The U.S. has asked member nations to sign a declaration on U.N. reforms, and more than 100 have done so. The president wants the U.N. to cut spending and make other operational changes.

Nikki Haley, the U.S. ambassador to the U.N., said Trump’s criticisms were accurate at the time, but that it is now a “new day” at the U.N. An organization that “talked a lot but didn’t have a lot of action” has given way to a “United Nations that’s action-oriented,” she said, noting the Security Council votes on North Korea this month.

Guterres has proposed a massive package of changes, and Haley said the U.N. is “totally moving toward reform.”

“We said that we needed to get value for our dollar and what we’re finding is the international community is right there with us in support of reform. So it is a new day at the U.N.,” she said Sunday on CNN’s “State of the Union.” She said Trump’s pleas had been heard and “what we’ll do is see him respond to that.”

North Korea is expected to be key among the issues Trump will discuss at the General Assembly as tensions reach a new peak.

Video released overnight shows United States and South Korea warplanes dropping live bombs during drills over the Korean Peninsula. This latest show of force followed Friday’s missile test by North Korea.

Secretary of State Rex Tillerson appeared on “Face The Nation” Sunday, a day after North Korea released a new image of its leader, Kim Jong Un, observing a recent missile test.

“The president has been very clear that he views this threat of North Korea as ever growing,” Tillerson said.

Tillerson said it’s up to North Korea to avoid the U.S. taking military action.

“All they need to do to let us know they’re ready to talk is to just stop these tests, stop these provocative actions,” he said.

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Haley went a step further.

“If the United States has to defend itself or defend its allies in anyway, North Korea will be destroyed,” she said. “We are trying every other possibility that we have.”

Another key topic expected to come up during the president’s visit is the Paris climate accord, which Trump pulled out of earlier this year.

National Security Adviser H.R. McMaster says reports that the president has changed his mind about leaving the agreement are not true.

“He said at some point in the future, if there can be, if there can be a deal that addresses these fundamental flaws he’s open to it,” he said.

Trump more recently has praised a pair of unanimous council votes to tighten sanctions on North Korea over its continued nuclear weapon and ballistic missile tests.

Trump also planned to hold separate talks Monday with Israeli Prime Minister Benjamin Netanyahu and French President Emmanuel Macron. McMaster said the conversations would be wide-ranging, but that “Iran’s destabilizing behavior” would be a major focus of Trump’s discussions with both leaders.

Trump was also hosting a dinner for Latin American leaders. McMaster said Venezuela, which has been gripped by economic and political turmoil, will be discussed.

The U.N. General Assembly takes place through Thursday under tight security. NYPD Deputy Commissioner of Intelligence and Counterterrorism John Miller called it one of the most complex security operations the NYPD carries out every year.

“People who live here are kind of used to it,” he said.

Drivers can expect closures and detours on the east side of Manhattan in the vicinity of 1st Avenue between 48th and 42nd streets as well as side streets around the U.N.

A handful of hotels and Trump Tower are also frozen.

“Members of the public will also see a number of check points,” said NYPD Manhattan South Chief Bill Morris. “There are actually 11 checkpoints.”

Morris said the same officers will staff the checkpoints every day to minimize confusion. That is all to make sure 126 heads of state are safe as they get to and from the UN headquarters.

“But because of all of these movements of that number of motorcades, people are going to find themselves easily getting in to traffic situations that it is not as easy to get out of,” Miller said.

Thus, officials advised the best idea is not to try to drive into Midtown this week.

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(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)