PRESIDENT Donald Trump has made his debut at the United Nations, using his first speech to urge the 193-nation organisation to cut red tape and more clearly define its global mission.

But while Mr Trump chastised the UN — an organisation he sharply criticised as a candidate for president for its spiralling costs — he said the US would “pledge to be partners in your work” in order to make the UN “a more effective force” for peace.

“In recent years, the United Nations has not reached its full potential due to bureaucracy and mismanagement,” said Mr Trump, who rebuked the UN for a ballooning budget. “We are not seeing the results in line with this investment.”

The US covers about 22 per cent of the UN budget.

TRUMP PLUGS HIS TOWER

However the billionaire opened his remarks by plugging his nearby residential tower, the Trump World Tower.

Built in 2001, the residential skyscraper in the United Nations Plaza was briefly the tallest all-residential tower in the world.

“I actually saw great potential across the street, to be honest with you, and it’s only for the reason that the United Nations was here that that turned out to be such a successful project,” Mr Trump said, after an introduction from UN Ambassador Nikki Haley.

CBS: At his first visit at UN #Trump started by praising Trump Tower across the street - it "turned out to be such a successful project" pic.twitter.com/7a4VA7zcUK — Tom Sabin (@TomSabinNYC) September 18, 2017

PRESIDENT CALLS FOR REFORM

After the brazen plug, the president pushed the UN to focus “more on people and less on bureaucracy” and to change “business as usual and not be beholden to ways of the past which were not working” while also suggesting that the US was paying more than its fair share to keep the New York-based world body operational.

But he also complimented the steps the UN had taken in the early stages of the reform process and made no threats to withdraw his nation’s support.

Speaking briefly with reporters, Mr Trump riffed off of his campaign slogan, Make America Great Again, saying his main message is: “Make the United Nations great. Not again. Make the United Nations great. Such tremendous potential, and I think we’ll be able to do this.”

His tone stood in stark contrast to his last maiden appearance at a global body, when he stood at NATO’s new Brussels headquarters in May and scolded the member nations for not paying enough and refusing to explicitly back its mutual defence pact.

BISHOP BACKS TRUMP ON REFORM

Australian Foreign Minister Julie Bishop welcomed Mr Trump’s backing of UN reform.

“If there are ideas and ways that we can improve the performance of the United Nations, then of course Australia would welcome them,” she told reporters in New York.

“We want to ensure it is the most effective, efficient organisation it can be and we were pleased that President Trump has supported UN reform.”

Promoting Aust interests & priorities at #UNGA #NewYork - largest gathering of world leaders & foreign ministers https://t.co/ZkL6VQAnDD pic.twitter.com/VoJxiTtd4K — Julie Bishop (@JulieBishopMP) September 15, 2017

Ms Bishop is scheduled to make her address on behalf of Australia on Friday, and will hold bilateral meetings on Monday with Japanese Foreign Minister Taro Kono, Swiss Foreign Minister Didier Burkhalter and Israeli Foreign Affairs Minister Yuval Rotem.

Prime Minister Malcolm Turnbull would traditionally make the annual trip to New York, but with the citizenship controversy hanging over Deputy Prime Minister Barnaby Joyce he decided to stay in Australia.

TRUMP’S HISTORY WITH UN

While running for office, Mr Trump labelled the UN as weak and incompetent, and not a friend of either the US or Israel. But he has softened his tone since taking office, telling ambassadors from UN Security Council member countries at a White House meeting this year that the UN has “tremendous potential.”

Mr 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.

Mr Trump’s big moment comes on Tuesday, when he delivers his first address to a session of the UN General Assembly.

The annual gathering of world leaders will open amid serious concerns about Mr Trump’s priorities, including his policy of “America First,” his support for the UN and a series of global crises. It will be the first time world leaders will be in the same room and able to take the measure of Mr Trump.

The president on Monday praised UN Secretary-General Antonio Guterres, who also spoke at the reform meeting and said he shared Mr Trump’s vision for a less wasteful UN to “live up to its full potential.”

The US has asked member nations to sign a declaration on UN reforms, and more than 120 have done so.