António Guterres, the former prime minister of Portugal who took over as secretary general of the United Nations on 1 January, told staff at the organisation's headquarters on Wednesday that the UN cannot be expected to work miracles.
"I know that the way the election process went generated high expectations," Guterres said. "I think it's useful to say that there are no miracles and I am certain that I am no miracle worker.
"The only way to achieve our objectives is to work together as a teach and earn the right to serve the global values enshrined in the [UN] Charter, which are the UN's values and the values that unite humanity."
The secretary general made the comments to several dozen members of staff who were awaiting him when he entered UN headquarters in New York.
Guterres had started by warning against any "illusions", recalling the New Year's Eve massacre in Istanbul, which claimed 39 lives.
"You can imagine how it is for me, having worked as High Commissioner with the people of Turkey, the country that has come to host the world's largest number of refugees, to see that they have now become victims of this terrible terrorist attack," he said.
Looking back over recent decades, Guterres noted that while the number of people in extreme poverty have fallen and welfare has increased, "the truth is that social inequalities have increased".
In a globalised world, he argued, "the fact of your being excluded makes it still more unbearable."
Guterres also made reference to growing attacks on multilateralism by nationalist politicians - which could be one of the big challenges during his term as secretary general - barely two weeks before Donald Trump is to take office as US president on 20 January.
"This is the Este moment in which we must affirm the value of multilateralism," he said. "This is the moment in which we must recognise that only global solutions can resolve global problems and that the UN is the cornerstone of this multilateral approach."