The former RoK foreign minister, 62, takes over on January 1, succeeding Kofi Annan, 68, who steps down at the end of the month after 10 years as UN leader.

"You could say that I am a man on a mission. And my mission could be dubbed 'Operation Restore Trust': Trust in the organization and trust between member-states and the secretariat," Mr Ban said.

“I hope this mission is not 'Mission Impossible,'" he told reporters after taking the oath of office before the 192-nation UN General Assembly.

Mr Ban lavished praise on Annan, saying his tenure was marked by "high ideals, noble aspirations and bold initiatives."

Key tasks, Mr Ban said, will include injecting new life into a "sometimes weary" secretariat staff and setting "the highest ethical standard."

At a news conference following his swearing in, Ban was short on policy specifics and said he would make no staff appointments until after the start of the year. But he indicated he was searching for a woman to be Deputy Secretary General.

Reuters