Sarah F. Cliffe, a former United Nations assistant secretary general who is now director of the Center on International Cooperation, a research organization at New York University, said she expected a reprise of the tensions that erupted between the United States and the United Nations during the administration of President George W. Bush. John R. Bolton, who was ambassador to the United Nations under Mr. Bush, once said the United Nations would be more effective without its top 10 floors, where its senior leaders have their offices. Mr. Bolton is one of Mr. Trump’s many would-be candidates for secretary of state.
But Ms. Cliffe said Mr. Trump may also find the United Nations useful.
“He prides himself on making deals,” she said. “The U.N. is the forum where countries make deals in their own national interests but that also does some collective good.”
His own comments about the United Nations are difficult to parse. At a 2005 Senate hearing about planned renovations of the United Nations headquarters, he described himself as “a big fan” and said that “the concept of the United Nations and the fact that the United Nations is in New York is very important to me and very important to the world as far as I am concerned.”
As one of Manhattan’s pre-eminent builders, he also offered to handle the renovation at half the price. In 2012, he complained on Twitter about the marble behind the speaker’s lectern at the General Assembly hall, claiming he could build it better.
Whatever his specific views, a number of statements made by Mr. Trump and his loyalists have conflicted with the values and positions of the United Nations. Here are the major examples:
Mr. Trump, who has called climate change a hoax, has suggested he would withdraw the United States from the Paris accord, widely regarded as the most important United Nations achievement in years. Secretary General Ban Ki-moon and President Obama invested a great deal of political energy in its success.
This past week, speaking in Marrakesh, Morocco, at an international meeting on climate change, Mr. Ban said he had spoken by telephone with Mr. Trump and looked forward to a personal meeting about the importance of saving the planet from environmental disaster.
“As president of the United States, I am sure that he will understand this, he will listen, he will evaluate his campaign remarks,” Mr. Ban said.
Even if Mr. Trump does not withdraw the United States from the accord, he could ignore important commitments, including cuts in carbon emissions or contributions to a global fund to help poor countries deal with the damage wrought by climate change. American disregard of the accord could cause other countries to renege on their promises as well.
Diplomats are trying to convince the Trump transition team that adhering to the deal is good for American businesses.
Refugees and Migrants
Mr. Trump has said he wants to bar entry to refugees from certain countries, and his campaign has defended a widely pilloried Twitter message by his son, Donald Trump Jr., comparing Syrian refugees to poisoned Skittles.
Barring refugees based on where they come from would be in blatant violation of international law, which requires countries to offer protection to all those fleeing war and persecution. Mr. Trump’s proposal has already been denounced by the United Nations high commissioner for human rights, Zeid Ra’ad al-Hussein, who said during the campaign that Mr. Trump would be “dangerous from an international point of view.”
The incoming United Nations secretary general, António Guterres, was even more pointed. He said that any proposal to restrict Muslim refugees would only help jihadist organizations spread their propaganda and recruit followers. “It’s just telling them: ‘You are right. We are against you.’ ”
He is to take office less than three weeks before Mr. Trump.
Iran Nuclear Agreement
Mr. Trump has repeatedly threatened to scrap the agreement reached last year between Iran and six world powers, including the United States, that severely limited Iran’s nuclear activities in exchange for sanctions relief.
Mr. Ban has expressed the opposite view, calling the agreement a triumph of diplomacy that reduced the threat of war. He has urged all participants to respect its provisions.
The agreement was also endorsed by the Security Council in a unanimous resolution.
Almost immediately after the agreement was announced in July 2015, Mr. Trump expressed his hostility in a Twitter post.
At that same March meeting of the American Israel Public Affairs Committee, a lobbying group, Mr. Trump asserted that “my No. 1 priority is to dismantle the disastrous deal with Iran,” arguing that the Iranians had outsmarted the United States in winning concessions and could still develop a nuclear weapon when the pact’s restrictions expire in 15 years.
Despite Mr. Trump’s assertions, it remains unclear whether he will seek to annul or amend the nuclear agreement. The other countries involved — Britain, China, France, Germany, Iran and Russia — have all expressed their intention to honor it.
Senator Bob Corker, a Tennessee Republican who is under consideration for a cabinet post in the new administration, said Mr. Trump would probably be cautious about any change of policy.
“I don’t think he will tear it up, and I don’t think that’s the way to start,” Mr. Corker said on CNN.
Kris Kobach, a member of Mr. Trump’s transition team, has suggested that the new administration could create a national registry for immigrants from countries where terrorist groups are active. That would go against an international convention on nondiscrimination, which took effect nearly 50 years ago.
Western powers have sought to use the United Nations to highlight rights abuses they attribute to President Bashar al-Assad of Syria. Mr. Trump has made clear that whatever war crimes Mr. Assad may have carried out, Mr. Trump’s first priority is the Islamic State. “I don’t like Assad at all, but Assad is killing ISIS,” he said in October. “Russia is killing ISIS. And Iran is killing ISIS.”
Arms Trade Treaty
Mr. Trump has not specified his view on the Arms Trade Treaty, which was overwhelmingly adopted in 2013 by the General Assembly and entered into legal force nearly two years ago. But gun-rights advocates in the United States led by the National Rifle Association, one of Mr. Trump’s most powerful supporters, strongly criticized the treaty and vowed to ensure that the Senate never ratifies it.
The treaty is an attempt to regulate the enormous global trade in conventional weapons, and for the first time it links sales to the human rights records of the buyers.
The N.R.A. has argued that the treaty’s provisions amount to an infringement of the Second Amendment. Kelly Ayotte, a Republican senator from New Hampshire who is among those being talked about as Mr. Trump’s potential ambassador to United Nations, has been an outspoken critic of the treaty.
Israel and Palestinians
Mr. Trump’s precise views are unclear on this question, which has vexed the United Nations for decades. But he has said he is “100 percent” in favor of moving the United States Embassy from Tel Aviv to Jerusalem, the holy city that Israel claims as its undivided capital. Such a change would be a major break from longstanding American policy and would infuriate the Palestinians, who want at least part of Jerusalem to be the capital of a future Palestinian state. The secretary general has called Jerusalem “the heart of any negotiated solution to the question of Palestine.”
Relations With Cuba
Mr. Trump has sharply criticized President Obama’s reconciliation with Cuba, a change that was widely welcomed at the United Nations, where an annual resolution condemning the American trade embargo with Cuba passes overwhelmingly. Mr. Trump’s running mate, Mike Pence, has vowed that the new administration’s policy will be much tougher.