United Nations Secretary-General Kofi Annan will on Wednesday play host to US President George Bush, Russian President Vladimir Putin and Chinese President Hu Jintao.
He will also meet nearly 50 prime ministers, including Britain's Tony Blair, France's Dominique de Villepin and Japan's Junichiro Koizumi during the three-day gathering.
The world leaders will be tasked with endorsing the 35-page reform document approved by the UN General Assembly after months of hard bargaining.
The reform package sought to strike a balance between fighting global poverty and battling terrorism, while promoting human rights, preventing genocide and UN management reforms.
But Annan will lead the summit under the cloud of the oil-for-food scandal that has tarnished his image and that of the world body.
An independent panel last week cleared the UN chief of ethical lapses, but documented administration failings and evidence of corruption in the UN's $100-billion humanitarian scheme.
No disarmament agreement
The package agreed to on Tuesday showed how far apart rich and poor nations remained on how to approach a host of issues, including human rights, UN management practices, and disarmament, which was left out altogether.
Annan (L): Failure to agree on
disarmament a real disgrace
"We didn't get everything we wanted," said Annan, who had presented a much-more ambitious plan to reform the institution. "But we can build on it," he added.
Annan said that the failure to find common ground on disarmament was "a real disgrace".
US officials had pushed hard for UN management reforms and the creation of a new Human Rights Council.
US Undersecretary of State Nicholas Burns also said Washington "didn't get everything we wanted", adding that it "had to compromise".
Burns said that it is "not a 100% victory, but it's a very good beginning... There is some unfinished business. We have to come back in a few months."
Britain's UN envoy Emyr Jones Parry said on behalf of the European Union that the compromise document "is a tremendous achievement".
"It means that the summit can start on a correct basis," he added. "For us the challenge will be ... to actually maintain the progress of what has been agreed today."
Non-governmental organisations, which have been monitoring the negotiations, complained that the proposed reforms were not bold enough.
"In terms of an ambitious moment, we haven't got it," said Nicola Reindorp of the British charity Oxfam International.
"If this was meant to be the big moment of governments reviewing how they are going to achieve the Millennium Development Goals, by any stretch of the imagination they failed on this point"
"If this was meant to be the big moment of governments reviewing how they are going to achieve the Millennium Development Goals, by any stretch of the imagination they failed on this point."
The reform document was approved on Tuesday as Swedish diplomat Jan Eliasson succeeded Gabon's Jean Ping as chairman of the incoming General Assembly's 60th session.
On the sidelines of the summit, the leaders were to hold a series of bilateral meetings.
Bush was to meet with Blair, his closest ally in the war in Iraq, attend a UN Security Council summit, and attend the launch of the UN Democracy Fund, which aims to help countries hold elections.
The US leader was also to discuss the Middle East peace process with Israeli Prime Minister Ariel Sharon in their first meeting since Israel's "disengagement" from the Gaza Strip.
Blair's "incitement" initiative
In the meantime, Bush, Hu, Putin, Blair, Koizumi and de Villepin are among those due to participate in a rare high-level meeting of the 15-nation UN Security Council at which a resolution on the "incitement of terrorism" is to be adopted.
"The resolution's sponsors have made it easy for abusive governments to invoke the resolution to target peaceful political opponents, impose censorship and close mosques, churches and schools"
Kenneth Roth, Human Rights Watch executive director
The meeting coincides with a UN gathering in New York of some 150 world leaders to address the challenges of global multilateral action in the 21st century.
The global initiative on terrorism was proposed by Blair, who is pursuing a similar crackdown in Britain following July attacks by four bombers who killed themselves and 52 others in London.
Saying the attacks had altered the British landscape, Blair on 5 August put forward plans to ban two Islamic groups and empower the authorities to expel or exclude foreign nationals who allegedly "incited violence or glorified terrorism".
But the New York-based Human Rights Watch said the resolution, which has eight co-sponsors, would give governments a pretext to suppress peaceful expression.
Open to abuse
The proposed resolution offers no definition of what constitutes "incitement to commit" terrorist acts and urges governments not only to outlaw such actions but also to "prevent such conduct".
"Those who incite others to commit terrorism must be prosecuted.
"But the resolution's sponsors have made it easy for abusive governments to invoke the resolution to target peaceful political opponents, impose censorship and close mosques, churches and schools," said Kenneth Roth, Human Rights Watch executive director.