We have come to a decisive moment in history. The great threat of nuclear confrontation between rival superpowers is now behind us. But a new and diverse constellation of threats has arisen in its place. We need to look again at the machinery of international relations. Is it up to these new challenges? If not, how does it need to be changed?

The events of the last year have exposed deep divisions among members of the United Nations on fundamental questions of policy and principle. How can we best protect ourselves against international terrorism and halt the spread of weapons of mass destruction? When is the use of force permissible — and who should decide? Does it have to be each state for itself, or will we be safer working together? Is "preventive war" sometimes justified, or is it simply aggression under another name? And, in a world that has become "unipolar," what role should the United Nations play?

These new debates come on top of earlier ones that arose in the 1990s. Is state sovereignty an absolute and immutable principle, or does our understanding of it need to evolve? To what extent is it the international community's responsibility to prevent or resolve conflicts within states (as opposed to wars between them) — particularly when they involve genocide, "ethnic cleansing" or other extreme violations of human rights?

These questions cannot be left unanswered. Yet they are not the only questions. And for many people they may not even be the most urgent.

In fact, to many people in the world today, especially in poor countries, the risk of being attacked by terrorists or with weapons of mass destruction, or even of falling prey to genocide, must seem relatively remote compared to the so-called "soft" threats — the ever-present dangers of extreme poverty and hunger, unsafe drinking water, environmental degradation and endemic or infectious disease.

Let's not imagine that these things are unconnected with peace and security, or that we can afford to ignore them until the "hard threats" have been sorted out. We should have learned by now that a world of glaring inequality — between countries and within them — where many millions of people endure brutal oppression and extreme misery is never going to be a fully safe world, even for its most privileged inhabitants.

Today, the common ground we used to stand on no longer seems solid. In seeking new common ground for our collective efforts, we need to consider whether the United Nations itself is well suited to the challenges ahead.

During the last year, the United Nations has been held under a microscope. In an atmosphere of acrimony surrounding the crisis in Iraq, the importance and, indeed, the relevance of the institution have in some quarters been called into question. This was especially true at the time of the United States decision to go to war in Iraq without the explicit approval of the Security Council.

I know that over the years our record has been far from perfect. The Security Council has been unable to prevent horrendous atrocities — the rule of the Khmer Rouge in Cambodia, ethnic cleansing in the former Yugoslavia, genocide in Rwanda. But, to paraphrase Henry Cabot Lodge, the United Nations may not have brought us to heaven but it played a vital role in saving us from hell.

Peace was brought to many lands through the U.N. — Cambodia, El Salvador, Guatemala, Mozambique. We helped protect against a drift toward nuclear holocaust, including during the Cuban missile crisis. We served as a vehicle for action against North Korea, against Iraq after the invasion of Kuwait. We've brought relief to millions affected by fighting, famine and floods, and we have helped reduce child mortality and eradicate smallpox. We were critical in helping the developing world throw off the yoke of colonialism.

To my mind, recent events have only underlined the need for the United Nations. That's why I convened a panel, chaired by former Prime Minister Anand Panyarachun of Thailand, to examine the future of our organization. The panel holds its first meeting this weekend.

Its role is threefold: to analyze current and future threats to peace and security; to assess the contribution that collective action can make in meeting these threats; and to recommend the changes needed to make the United Nations a legitimate and effective instrument for a collective response. How, in particular, can the United Nations "take effective collective measures for the prevention and removal of threats to the peace," which is one of its purposes, as defined in Article I of its charter? I hope the panel will complete its report by autumn 2004.

If it does its work well, history may yet remember the current crisis as a great opportunity that wise men and women used to strengthen the mechanisms of international cooperation and adapt them to the needs of the new century.