In his debut at the United Nations, President Donald Trump told the organization it was failing to live up to its potential and urged the organization to take a “bold stand” with a more clearly defined global mission.

"Focus more on people, less on bureaucracy," he told a special meeting on reform on September 18 at UN headquarters in New York. "It has not reached its potential because of the bureaucracy and mismanagement."

Trump, a frequent critic of the UN, was frank in laying out his views on how to improve the world body a day before he makes his first address to the 193-member General Assembly, which holds its annual General Debate session from September 19 to 25.

UN Secretary-General Antonio Guterres responded to Trump’s message by saying he agreed that bureaucracy was an issue that kept him awake at night.

"Someone out to undermine the UN could not have come up with a better way to do it than by imposing some of the rules we have created ourselves," he said.

Part of Trump’s disapproval stems from the cost of the UN to American taxpayers.

Washington, the biggest UN financial contributor, has threatened deep funding cuts that Guterres has said would create an "unsolvable problem" for the organization.

In June, the General Assembly voted to cut $600 million from the organization's nearly $8 billion annual peacekeeping budget amid pressure from the Trump administration.

Trump reiterated his concerns on September 18, saying that the United States was “not seeing results in line with U.S. investment.”

"The United Nations must hold every level of management accountable, protect whistleblowers. and focus on results rather than on process," Trump said.

"I am confident that if we work together and champion truly bold reforms the United Nations will emerge as a stronger, more effective, more just, and greater force for peace and harmony in the world," he added.

Also on September 18, Trump is scheduled to hold talks with French President Emmanuel Macron and Israeli Prime Minister Benjamin Netanyahu, as well as a "working dinner" with Latin American leaders.

White House spokeswoman Sarah Sanders said at a briefing on September 15 that while Trump's talks with Netanyahu and Macron "will be wide-ranging. We expect that Iran's destabilizing behavior, including its violation of the sovereignty of nations across the Middle East, to be a major focus."

Both Macron and Netanyahu were expected to raise the 2015 deal under which Iran has curbed its nuclear activities in exchange for sanctions relief, with Macron making a case for keeping it alive and Netanyahu pushing for its demise.

On September 14, Trump repeated his charge that Iran is violating "the spirit" of the agreement.

About 130 world leaders will attend this year's General Assembly’s debate session.

With reporting by AFP, dpa, Reuters, Interfax, and TASS