"I urge you, as world leaders, individually collectively, to keep working on this reform agenda to have patience to persevere, and the vision needed to forge a real consensus," the UN secretary-general told the more than 170 leaders attending a three-day summit on Wednesday.
His plea came a day after the UN General Assembly adopted a watered-down version of his ambitious reform plan for the scandal-tainted United Nations.
"By your agreement on the outcome document, these achievements will be locked in," he added.
"No matter how difficult agreement is, there is no escaping the fact that the challenges of our time must be met by action and today, more than ever, action must be collective if it is to be effective."
And in a veiled reference to the United States, he said: "Whether our challenge is peacemaking, nation-building, democratisation or responding to natural or man-made disaster, we have seen that even the strongest amongst us cannot succeed alone."
The UN chief, whose second five-year term expires at the end of 2006, also stressed the need to restore his credibility and that of his organisation, which have been tarnished by the Iraq oil-for food scandal and sexual misconduct by UN peacekeepers.
"We must restore confidence in the organisation's integrity, impartiality and ability to deliver"
UN Secretary-General Kofi Annan
Last week, Annan took personal responsibility for the administrative failings in the management of the $100-billion Iraq programme but vowed he would not give in to critics in the US Congress.
"I am ready to work with you on the challenges that remain, on implementing what has been agreed, and on continuing to reform the culture and practice of the secretariat," said the secretary-general, who faces intense US pressure to tighten UN management practices.
"We must restore confidence in the organisation's integrity, impartiality and ability to deliver."
He singled out the fight against global poverty as a priority in the reform agenda adopted after six months of hard bargaining.
Annan bemoaned the failure of
states to address nuclear spread
"Most important of all, an additional $50 billion per year has been unleashed to fight poverty by 2015," he noted, highlighting a commitment by rich nations to meet the goal of earmarking 0.7% of gross national product as development aid to poor nations by 2015.
But he also bemoaned the failure of member states to address the threat of nuclear proliferation in the document endorsed on Tuesday.Posturing preventing results
"Twice this year, at the NPT (nuclear Non-Proliferation Treaty) review conference, and now at the summit, we have allowed posturing to get in the way of results," Annan said.
"This is inexcusable. Weapons of mass destruction pose a grave danger to us all, particularly in a world threatened by terrorists with global ambitions and no inhibitions."
He urged countries to resume negotiations on this crucial issue.
"This package is a good start. On some issues, we have real breakthroughs. On others, we have narrowed our differences and made progress. On others we remain worryingly far apart."
The UN called for support for Swedish diplomat Jan Eliasson, chairman of the incoming 60th General Assembly session, pushing for the speedy creation of a revamped Human Rights Council, a peace-building commission to assist countries emerging from conflict and conclusion of a comprehensive convention on terrorism.