UN leader Ban Ki-moon formally put himself forward for a second five-year term on Monday and diplomats said his re-election could be wrapped up by the end of the month.
The 66-year-old former South Korean foreign minister said he would make the battle against climate change his top priority and defended the way he deals with world powers on issues such as human rights.
Ban told a press conference he had sent a letter to the 192 UN member states to "humbly" offer himself for a new term.
"It has been an enormous privilege to lead this great organisation. If supported by the member states, I would be deeply honoured to serve once more," he said.
Ban took over as secretary general from Kofi Annan in 2007. Diplomats say that with no challenger in sight, the UN Security Council should quickly give approval for a second term and the UN General Assembly will hold a formal vote before the end of June.
China and France, among the five permanent members of the Security Council, quickly came out in support of Ban's bid.
"China applauds his work as the secretary general," said China's foreign ministry spokesman Hong Lei in Beijing. "Mr Ban has made great contributions in promoting the UN to play a greater role in international affairs."
French Foreign Minister Alain Juppe said: "For the last five years, the secretary general has shown faultless commitment to the service of the United Nations, peace, and also development. He has shown courage and determination in a period of crisis."
Ban said his first term had been an "extraordinary challenge" for the United Nations.
"We can be proud of what we accomplished together. We have raised climate change to the top of the global agenda, we have responded quickly and effectively in areas of devastating humanitarian emergencies" in Myanmar, Haiti, Pakistan and elsewhere, the UN chief said.
"We have saved many lives and sowed the seeds of peace in Sudan, Somalia, Democratic Republic of Congo and Cote d'Ivoire. They must be nurtured."
The UN leader said climate change would remain his top priority in any second term.
"I will spare no effort," Ban said, defending his record in the troubled climate talks during his first five years. "This is the most important priority for human beings."
Ban has faced most criticism as UN leader for his reluctance to tackle the Security Council permanent members - Britain, China, France, Russia and United States - over issues such as rights.
When asked at the press conference whether he would be tougher with the permanent powers, Ban said: "I would like to make it quite clear when it comes to universal human rights there is no such distinction or difference."
He also said that China must improve its human rights.
Ban has been criticised by rights groups about his use of "quiet diplomacy" with China and other major nations.
But the UN secretary general insisted that he has always spoken out on human rights, which he called a "cornerstone" of the UN charter.
"I have been speaking with them (China) constantly about improvement, the necessity of improvement of human rights in China," Ban told the press conference.
"I will continue to discuss this matter wherever it happens."
Ban was notably criticised after a visit to China last November when he failed to raise the case of jailed Nobel Peace prize winner Liu Xiaobo in a meeting with China's President Hu Jintao.
He highlighted his record speaking out on Sri Lanka, where he set up a panel of experts to look into the deaths of thousands of civilians in a military campaign against Tamil separatists.
Ban has also been outspoken criticising leaders of Arab nations facing uprisings in recent months.
- AFP/de
