As President-elect Donald Trump moves closer to his January inauguration, many at the United Nations could be excused for being worried given his critical pronouncements on the world body over the years.

Trump's views are at odds with the U.N. on a variety of issues – ranging from the Iran nuclear deal to the Paris climate treaty to the resettling of millions of refugees.

Well aware of those differences, outgoing U.N. Secretary-General Ban Ki-moon sent Trump a congratulatory note emphasizing that the U.N. will be counting on him "to strengthen the bonds of international cooperation as we strive together to uphold shared ideals, combat climate change, advance human rights, promote mutual understanding ... to achieve lives of peace, prosperity and dignity for all."

During the presidential campaign, Trump sent a strong and unequivocal message to the U.N. at the annual American Israel Public Affairs Committee (AIPAC) conference in Washington, D.C.

"The United Nations is not a friend of democracy, it's not a friend to freedom, it's not a friend even to the United States of America where, as you know, it has its home, and it is surely not a friend to Israel," Trump said in March.

Former U.S. Ambassador to the United Nations John Bolton told Fox News the U.N. could be bracing for a different relationship with the Trump White House. 

"The overwhelming feeling among most members was Barack Obama was their kind of U.S president, so I do think it will be a different reception. The whole point of the idea of making America great again is to reassert ourselves especially in bodies like the United Nations," he said.  

Bolton, who is rumored to be in consideration for a senior role in the Trump administration, predicts the president-elect will take a hard look at the world body. He believes that as the biggest contributor to the United Nations -- giving almost $3 billion a year – the U.S. has room for cuts.

"I think some of it is spent quite well, some of the specialist agencies do an excellent job, but much of it frankly is wasted on bureaucracy and peacekeeping operations that have outlived their usefulness on a range of programs that just exist from continuing inertia," he told Fox News. "So I think a good hard look at the U.N. budget is long overdue and I wouldn't be at all surprised if a President Trump once in office does pay particular attention to it."

Trump’s U.N. concerns aren’t new. In a 2006 interview with Fox News’ Eric Shawn, Trump said the multi-billion dollar renovation of the world body's headquarters in Manhattan was "total insanity."

Trump's choice of Tea Party favorite Nikki Haley, the Republican governor of South Carolina, to be his ambassador to the United Nations could send shudders through the halls of the U.N., in part because Haley is known to be a stalwart ally of Israel -- a country many critics say has been regularly and unfairly singled out by the U.N. as the institution has routinely ignored some of the world's worst human rights offenders.

"I think there's a lot of day-to-day issues that she doesn't know about -- the problem Nikki Haley is going to face is that many of the other countries’ delegates are people who have been there for a very long time. Her counterpart from Russia has been there for 10 years. So I think hitting the ground running will be important," said Martin Edwards, a professor at the School of Diplomacy and International Relations at Seton Hall University.

Edwards is optimistic that Trump and the new secretary-general -- former Socialist Prime Minister of Portugal Antonio Guterres -- will be able to work together.

"He expressed a desire to reform the U.N. and he expressed a desire to build trust between the U.N. and member states so I think there's a lot to look forward to actually in this honeymoon period," Edwards said.

Bolton, on the other hand, believes Trump’s election victory presents a historic opening: "I think this is a huge opportunity for the incoming administration to make substantial changes at the U.N. [and] to pull back from the approaches from the Obama administration."

Fox News’ Eric Shawn contributed to this report. 

Ben Evansky is a Fox News Channel field producer, and is a U.S. Youth Soccer qualified coach.