UNITED NATIONS - What happens when more than 150 world leaders meet in two weeks at the U.N. Millennium Summit? Traffic gridlock in New York City, almost certainly. But far less sure is whether the largest-ever gathering of heads of state and government will be able to chart a new course for the United Nations to meet the challenges of the 21st century.
''It's easy to be cynical about these meetings and say, 'Oh, they produce nothing,''' Deputy Secretary-General Louise Frechette said at a news conference Thursday. ''But many such gatherings have made a real difference in focusing political energy and raising political will.''
That's what Secretary-General Kofi Annan and U.N. officials are hoping the Sept. 6-8 summit will produce - determination for an all-out effort to lift more than 1 billion people out of extreme poverty by 2015, to ensure that by that date all children everywhere can complete primary school, to reverse the AIDS epidemic by 2010, and to do a better job of preventing conflict and saving the environment.
''The purpose of this meeting is to deal with these problems. It's designed to generate a strong political commitment to reach these goals,'' Frechette said.
But that's just part of the summit agenda.
The secretary-general said in a report in April setting the stage for the summit that the greatest challenge today is to ensure that the information and technology revolution doesn't leave billions of people behind in squalor.
And the backdrop of the summit is globalization - not just its effects on the poor, but its effects on the United Nations.
''I think the reason for the secretary-general proposing this summit and the member states deciding to hold it is that we are going through a truly dramatic change in world relations, and there's a feeling that it's really very important for direction to be given at the highest level to this organization,'' Frechette said.
Britain's U.N. Ambassador Jeremy Greenstock said he believes the 188 U.N. members states ''have not fully come to terms with the growing effects of globalization on the current structure of world politics, which is based on national decision-making.''
There is a growing need for collective action to deal with global problems, he said, and ''the U.N. has to be stronger and more effective as the machine that deals with globalization.''
In his April report to world leaders, the secretary-general said the main role of the United Nations should be to stimulate collective action by governments, businesses, grassroots groups and foundations at the global level.
But whether a summit in which every leader gets to deliver a five-minute public speech and take part in one three-hour, off-the-record, roundtable discussion can address these complex issues remains to be seen.
Some diplomats say privately they fear it will generate millions of words and little action.
''I think the true significance of the meeting is that over 150 heads of state and government think the U.N. is important enough to take the bother to come here for two or three days,'' said Guatemala's U.N. Ambassador Gert Rosenthal, who helped organize the summit.
''I think they're signaling to the world that the U.N. is a worthwhile organization, that we need to strengthen it,'' he said. ''I don't think this is a historic meeting in terms of new departures.''
Within the summit, several mini-summits are also planned.
Leaders of the 15 countries on the Security Council will discuss peacekeeping issues, especially in Africa, on Sept. 7. At China's initiative, the five permanent council members - the United States, Britain, France, Russia and China - are also likely to hold their own summit the same day.
Hundreds of one-on-one meetings between leaders are expected as well.
On the summit sidelines, there will be a U.N. meeting for representatives of non-governmental organizations, a ''Dialogue of Civilizations'' being held at the initiative of Iranian President Mohammad Khatami, a summit of religious leaders, and a meeting of presiding officers of the world's parliaments.
In an effort to explain the upcoming traffic chaos to New Yorkers, the advertising agency Young and Rubicam has produced a television spot narrated by singer Harry Belafonte explaining the goals of the summit - with the message ''History is Made Here.''
Whether that happens, said New Zealand's U.N. Ambassador Michael Powles, ''depends on the leaders and political will.''