UNITED NATIONS, Dec. 14 -- South Korean diplomat Ban Ki Moon was sworn in Thursday as the United Nations' eighth secretary general in a ritualistic General Assembly ceremony as the United States and other countries praised Kofi Annan's 10-year stewardship of the world's premier political institution.

Ban, 62, said his priority when he takes office Jan. 1 is to restore public confidence and civility to a body that has been buffeted by corruption and sexual misconduct scandals, and has been riven by feuding over its future between its weakest and most powerful countries.

"You could say that I'm 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," Ban said at a news conference after the ceremony. "I hope this mission is not mission impossible."

Ban's remarks constituted an implicit rebuke of Annan, a Nobel Peace Prize laureate whose legacy was tarnished by his mismanagement of the agency's $64 billion oil-for-food program in Iraq. But Annan, who sat expressionless through much of the ceremony, received a rousing standing ovation and eulogistic tributes from representatives of Asian, African, European and Latin American countries.

Even the United States, whose outgoing ambassador, John R. Bolton, rarely had anything nice to say about Annan, bid an effusive farewell to the Ghanaian civil servant.

Alejandro D. Wolff, the acting U.S. ambassador, said Annan had been "a champion of human rights" and a defender of the poor and disadvantaged who "worked tirelessly" to serve "the millions of people who look to the U.N. to help them improve their lives."

"We salute today Secretary General Kofi Annan for his decade of dedicated service as the U.N.'s chief diplomat and administrator," he said, crediting Annan with backing some of Washington's most important foreign policy goals. He "has pushed the U.N. to do its part in the global struggle against extremism, proliferation of weapons of mass destruction, and terrorist threats."

But the focus of attention quickly shifted to Ban. He outlined his administrative and political priorities, saying he would move to resolve crises in North Korea; Darfur, Sudan; and the Middle East, including the "very hot and deteriorating situations in Lebanon and in Iraq, too."

He said he would select top officials primarily on the basis of merit, but would be mindful of the need to ensure geographical and gender balance in hiring. He said he will seek to identify a woman to serve as his deputy.

"One of my core tasks will be to breathe new life and inject renewed confidence into the sometimes weary [U.N.] secretariat," he said. "As secretary general, I will aim to reward the talent and skill of staff."

Ban said he will serve as a "bridge" between the rich and poor members, who have clashed over a range of issues, including revision of the U.N. bureaucracy and the promotion of human rights.

Ban sought to counter speculation that he is too discreet and cautious to confront the world's tyrants or stand up to the big powers. But he conceded that he can be evasive at times, recalling that the Korean news media had affectionately dubbed him the "Slippery Eel" because of how he can avoid answering sensitive questions.

"But that nickname was given because I was very friendly with the media. You should understand that. But I promise today that I can be a pretty straight shooter when I need to."

Ban sounded off on Iranian President Mahmoud Ahmadinejad's calls for the destruction of Israel and his hosting of a Holocaust conference that included many speakers who questioned the Nazis' mass murder of more than 6 million Jews.

"Denying historical facts, especially on such an important subject as the Holocaust, is just not acceptable. Nor is it acceptable to call for the elimination of any state or people," Ban said. "I'd like to see this fundamental principle respected both in rhetoric and practice by all the members of the international community."

He urged the international community to support Iraq's political transition, citing the "inability" of Iraqi authorities and the U.S.-led multinational force to "secure peace and security."

Ban stumbled as he tried to cross a critical rite of passage at the United Nations: speaking publicly in French, one of the institution's two official languages. Asked in French why that language merited its designation when more people speak Arabic or Chinese, Ban paused before asking the reporter to repeat the question slowly, saying in French that "it is very difficult for me, off the cuff, to reply in French." After hearing the question a second time, he called for an interpreter.