One year ago, US President George W. Bush stood before the United Nations General Assembly and threatened to go to war in Iraq with or without the international body's consent. The UN risked irrelevance if it refused, he said. Now, as 130,000 American troops struggle with rebuilding Iraq and protecting the country's infrastructure from guerilla attacks, at least one part of Mr Bush's prediction has come true. The US did go to war, without UN backing, by building its own 'coalition of the willing'. The irrelevance that he had forecast for the UN has not, however, materialised. If anything, the UN is looking increasingly crucial to the task of rebuilding Iraq and even Afghanistan, where the US only two years ago led an international force in dismantling the Taleban government. UN Secretary-General Kofi Annan was frank about the UN's challenges in his speech at the opening of the 58th General Assembly this week. He called for nothing short of an examination of how the UN is structured, and in particular the composition and functioning of the security council. If the delegates and members wanted the council to have any relevance at all, he told the gathering, they would have to resolve their differences about how the new council should look. The lack in recent years of principled and consistent answers to genocide, terrorism and proliferation of weapons of mass destruction has led to a credibility crisis that created an opening for the US to declare its doctrine of pre-emptive warfare. Mr Annan spoke of this doctrine more directly than ever before, saying it set a dangerous precedent but also that the UN must respond by looking at how it can better deal with the threats that have caused certain states to feel especially vulnerable and justify unilateral action. Mr Bush addressed the general sssembly on the same day, this time appealing for international support in the project of rebuilding Iraq and turning it into an anchor country within a democratic Middle East. Such a vision cannot come about without a reinvigorated United Nations. In the short term, the US will have to allow the UN to be meaningfully involved in reconstruction and peacekeeping in Iraq. Beyond that, it will be important to follow through with Mr Annan's plan to study how the UN can address global problems that have arisen since it was founded nearly six decades ago. If changes to the UN itself are called for, members should not hesitate to make them. This time around, the UN's relevance may well be at stake.