United Nations ? Starting his first day of work, new Secretary-General Ban Ki-moon vowed Tuesday to end mistrust of the United Nations and called for action to tackle “daunting” problems from crises in the Middle East and Darfur to reducing extreme poverty by half by 2015.

He renewed his promise to give priority to the North Korean nuclear issue and to defend human rights. When asked about Saddam Hussein’s execution, he said the victims of his crimes must not be forgotten, but he stressed the need to strengthen the rule of law.

Ban also announced that his first overseas trip will be to attend the African Union summit in Addis Ababa, Ethiopia, on Jan. 29-30 and hopes to meet Sudan’s President Omar al-Bashir there. He said he will meet his special envoy on Darfur, Jan Eliasson, today and put “my highest attention on this” issue in hopes of resolving the conflict peacefully.

Dozens of U.N. staffers applauded as the former South Korean foreign minister entered U.N. headquarters for the first time since he officially took over for Kofi Annan on New Year’s Day, a U.N. holiday. He immediately went to the Meditation Room and bowed his head in tribute to U.N. peacekeepers and staff members who died in service.

Speaking to reporters afterward, Ban said the huge media presence “is vivid proof that the United Nations is much alive and front-line addressing all the challenges and issues, and trying to give hope to all the people around the world.”

“It is a force to be reckoned with among governments and people everywhere,” he said.

“Unfortunately, the United Nations, though we have been playing pretty instrumental role for peace and prosperity and development, we have been underappreciated, sometimes unfairly criticized,” he said.

“I am determined to help my staff … to address all the challenges in the 21st century, and also by trying to bridge the gap and divide and distrust – mistrust – which have been plaguing too much the United Nations,” he said.

Ban said he was starting his first day “with much expectation and hope and promise.”

“I start my duties at a daunting time in international affairs, starting from Darfur to Middle East, Lebanon, Iran, Iraq, North Korea, many other crises that trouble our world from defending human rights and the need to step up our efforts to implement, to reach the target by 2015, the Millennium Development Goals,” he said. Those goals include halving extreme poverty, ensuring education, and stemming the AIDS pandemic.

“These challenges and issues needs to be addressed collectively, with collective wisdom and collective efforts,” he stressed. “Not a single person, including secretary-general of the United Nations, not a single country, however strong, powerful, resourceful may be, (can) address this.”