The Charter of the United Nations is categorical. "In order to ensure prompt and effective action by the United Nations," it confers on the Security Council "primary responsibility for the maintenance of international peace and security".
That responsibility can seldom have weighed more heavily on the members of the Council than it does this week. Within the next day or two, they have to make a momentous choice.
The context of that choice is an issue whose importance is by no means confined to Iraq: the threat posed to all humanity by weapons of mass destruction. The whole international community needs to act together to curb the proliferation of these terrible weapons, wherever it may be happening.
But the immediate and most urgent aspect of that task is to ensure that Iraq no longer has such weapons. Why? Because Iraq has actually used them in the past, and because it has twice, under its present leadership, committed aggression against its neighbours - against Iran in 1980, and against Kuwait in 1990.
That is why the Security Council is determined to disarm Iraq of these weapons, and has passed successive resolutions since 1991 requiring Iraq to disarm.
All over the world, people want to see this crisis resolved peacefully. They are alarmed about the great human suffering that war always causes, whether it is long or short. And they are apprehensive about the longer-term consequences that this particular war might have.
They fear that it will lead to regional instability and economic crises; and that it may - as war so often does - have unintended consequences that produce new dangers. Will it make the fight against terrorism, or the search for peace between Israelis and Palestinians, even harder? Will it sow deep divisions between nations and peoples of different faiths? Will it compromise our ability to work together in addressing other common concerns in the future?
Those are serious questions, and the answers must be carefully considered.
Sometimes it may be necessary to use force to deal with threats to the peace - and the Charter makes provision for that. But war must always be a last resort. It should be used only when every reasonable alternative has been tried - in the present case, only if we are sure that every peaceful means of achieving Iraq's disarmament has been exhausted. The United Nations, founded to "save succeeding generations from the scourge of war", has a duty to search for a peaceful solution until the last possible moment.
Has that moment arrived? That is the decision that the members of the Security Council now face.
It is a grave decision indeed. If they fail to agree on a common position, and some of them then take action without the Council's authority, the legitimacy of that action will be widely questioned, and it will not gain the political support needed to ensure its long-term success, after its military phase.
If, on the other hand, the members of the Council can come together, even at this late hour, and ensure compliance with their earlier resolutions by agreeing on a common course of action, then the Council's authority will be enhanced, and the world will be a safer place.
Let's remember that the crisis in Iraq does not exist in a vacuum. What happens there will have a profound impact on other issues of great importance. The broader our consensus on how to deal with Iraq, the better the chance that we can come together again and deal effectively with other burning conflicts in the world, starting with the one between Israelis and Palestinians. We all know that only a just resolution of that conflict can bring any real hope of lasting stability in the region.
Beyond the Middle East, the success or failure of the international community in dealing with Iraq will crucially affect its ability to deal with the no less worrying developments on the Korean peninsula. And it will affect our work to resolve the conflicts that are causing so much suffering in Africa, setting back the prospects for stability and development that that continent so badly needs.
Nor is war the only scourge that the world has to face. Whether they are protecting themselves against terrorism or struggling against the grim triad of poverty, ignorance and disease, nations need to work together, and they can do so through the United Nations. However this conflict is resolved, the UN will remain as central as it is today. We should do everything we can to maintain its unity.
All around the world, these last few months, we have seen what an immense significance not only States, but their peoples, attach to the legitimacy provided by the UN, and by the Security Council, as the common framework for securing peace. As they approach their momentous decision this week, I hope the members of the Council will be mindful of this sacred trust that the world's peoples have placed in them, and will show themselves worthy of it.
