More than 150 heads of state and government addressed the gathering but much of the real business was conducted away from the podium spotlight in sideline meetings that sought to thrash out solutions to old disputes and fresh challenges.
The pressing issue of Iran's nuclear ambitions was set to extend beyond the summit into the UN General Assembly, with a much anticipated speech on Saturday by Iran's new president, Mahmoud Ahmadinejad.
Ahmadinejad, who met with the British, French and German foreign ministers on Thursday, is to unveil proposals aimed at appeasing European and US concerns that Tehran is developing nuclear weapons.
The dominant summit theme of how to combat terrorism was taken up again on Friday by Indonesian President Susilo Bambang Yudhoyono, who called for greater international cooperation and a focus on the "true causes" of the problem.
"We in Indonesia believe that interfaith dialogue and empowering the moderates can reduce radicalism," said the leader of the world's most populous Muslim nation.
Australian Prime Minister John Howard noted that the pervasive shadow of terrorism had become "a grim but inescapable fact" and voiced disappointment that a watered-down document on UN reform adopted by the General Assembly on Tuesday had fallen short in addressing the terrorist threat.
"We in Indonesia believe that interfaith dialogue and empowering the moderates can reduce radicalism"
Susilo Bambang Yudhoyono,
The text of the document failed to establish an agreed definition of terrorism and left out a chapter on disarmament altogether - an omission branded a "real disgrace" by UN Secretary General Kofi Annan.
The issue of terrorism was put at the top of the summit's agenda from the very first day with Annan's opening speech and then by US President George Bush.
"The terrorists must know the world stands united against them," Bush said. "The lesson is clear, there can be no safety in looking away or seeking the quiet life by ignoring the hardship and oppression of others."
Talabani said Iraq was in
desperate need of help
The most impassioned plea came on Thursday from Iraqi President Jalal Talabani who said his country was in desperate need of help to confront terrorist "forces of darkness."
Talabani's appeal came amid a rising tide of violence across Iraq that has claimed nearly 200 lives in the past three days - most of them the victims of car bombs.
Annan opened the three-day summit with a frank assessment of the diluted UN reform document that boosted the UN commitment to eradicating poverty and genocide and promoting human rights, but was vague on details.
"We have not yet achieved the sweeping and fundamental reform that I and many others believe is required," Annan said.
The reform accord was to have been the crowning jewel of the summit, but ended up the target of withering criticism from human rights groups and development organisations who complained of a squandered opportunity.