Leading article: A decent man who took on an impossible job

It is impossible not to like and admire Kofi Annan, as he prepares to step down after 10 years at the helm of the United Nations. The first Secretary General to come from within the ranks of the world body, he is a transparently decent man, who has championed the cause of human rights more vigorously than any of his predecessors. There have been scandals on his watch, most notably the sexual harassment charges against Ruud Lubbers, the former UN High Commissioner for Refugees, and the mismanagement of the oil-for-food programme with Saddam Hussein's Iraq. But they have not lastingly sullied his reputation.

Mr Annan has been nobody's stooge - neither of the US, whose invasion of Iraq he called illegal, nor of the Third World countries who view the UN's newfound emphasis on human rights as neo-colonialism by another name. Insofar as it is possible for a single individual to be "the conscience of the world," Mr Annan has filled that role perhaps better than any of his predecessors.

But like them, he could not escape the realities of the job. The UN Secretary General heads no government and commands no armies. His authority is moral, his greatest power is that of the bully pulpit. Perhaps Kofi Annan on occasion did not speak from that pulpit loudly and forcefully enough. But even if he had, it would have made little difference.

The UN is ultimately no more than the sum of its parts, the 200-odd member countries. It is only as effective as its most important members - essentially the five veto-wielding permanent members of the Security Council - want it to be. And for all the platitudes about national boundaries dissolving in this age of globalisation, powerful countries have no intention of handing over serious sovereignty to the UN - or only under circumstances where the UN can be counted upon to support what they want to do.

The invasion of Iraq, the most blatant affront to the organisation during Mr Annan's tenure, illustrated this reality perfectly, as the US, the lone superpower, launched the war despite its failure to secure the consent of the UN, and the overwhelming disapproval of most of the rest of the world. Or take the genocides of the past two decades, which have been the greatest blot on the UN's reputation. The mass murders in Rwanda in 1994, at Srebrenica a year later, and now in Darfur, might have been prevented if the UN's members had given the organisation the means to do so. Yes, Mr Annan might have warned earlier and more vigorously about the unfolding genocide in south western Sudan. The fact of the matter, however, is that China, one of the "Big Five", has consistently blocked efforts to bring the government in Khartoum to account.

Plainly, the UN must be reformed. Mr Annan has made some modest progress in improving the organisation's bureaucracy. But the overhaul of the Security Council which he has proposed has yet to be put into effect. Until it is, the Council will continue to reflect the world as it was in 1945, not in 2006, with all the loss of representative legitimacy that implies.

In his valedictory speech yesterday in the US - the single country with whom smooth relations are most important if the UN is to function properly - he made the point eloquently. For all its imperfections, the UN offers the world the best hope of equitable governance, as a place where states can hold each other to account. It was especially important therefore, to organise it "in a fair and democratic way, giving the poor and the weak some influence over the actions of the rich and the strong". That is Mr Annan's dream. A dream, sadly, it is likely to remain.