During a formal ceremony at the General Assembly, Guterres will be sworn in before outlining in an address to all 193 UN member-states his plans to confront global crises and reform the 71-year-old United Nations.
The first former head of government at the UN helm, Guterres will take over from Ban Ki-moon on January 1, just weeks before President-elect Trump moves into the White House.
The choice of the former refugee chief as the ninth secretary-general energized many diplomats who see Guterres as a skilled politician, able to overcome divisions that have crippled the United Nations, notably over Syria.
Trump's election however is complicating that strategy.
More From This Section
"This is tough for Guterres," said Richard Gowan, a UN expert at the European Council on Foreign Relations. "He enjoyed a wave of diplomatic goodwill at the UN and looked set for a straightforward transition."
"Now he will find it hard to propose big institutional reforms or float new political initiatives until the Trump team is settled in and made its intentions clear."
Trump has not made any statements about his view of the United Nations or multilateralism since his election, but his choice of South Carolina Governor Nikki Haley as US ambassador was seen in some circles as a positive signal.
While Haley has no foreign policy experience, she has been a player in negotiating trade deals for her state and earned respect in foreign circles for taking a stand against racism by pulling the Confederate flag from the state capitol.
He will have to show that "he is shaking up the system enough in order to really make it effective, slimming it down in some places, realigning it in others, in a very pro-active way," said the diplomat, who asked not to be named.
The United States is by far the biggest financial contributor, providing 22 percent of the UN's operating budget and funding 28 percent of peacekeeping missions which currently cost USD 8 billion annually.