A United Nations summit marking the 60th anniversary of the United Nations opened on Wednesday with an appeal from Secretary-General Kofi Annan to world leaders to restore confidence in the world body and act together to meet the challenges of the 21st century.

Addressing over 150 presidents, prime ministers and monarchs gathered in the General Assembly chamber, Annan said the document they will be adopting at the end of the summit on Friday was 'a good start' but not 'the sweeping and fundamental reform' he proposed and he called for urgent action on the tough, unresolved issues.

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"Because one thing has emerged clearly from this process on which we embarked two years ago: whatever our differences, in our interdependent world, we stand or fall together," Annan said.

"Whether our challenge is peacemaking, nation-building, democratisation or responding to natural or man-made disasters, we have seen that even the strongest amongst us cannot succeed alone," he said in an apparent reference to the US difficulties in coping with the aftermath of Hurricane Katrina on the Gulf coast.

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Swedish Prime Minister Goran Persson, who is the summit co-chair, opened the high-level meeting with an appeal for collective action to prevent conflict and genocide and to protect human rights.

He warned that millions of lives will be lost if significant steps aren't taken now to fight global poverty 'and we will pass on a more unfair and more unsafe world to the next generation.'

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