Call it the Asian century, or the post-American age. Call it the return of history. Call it the decline of the West or the rise of the rest. By whichever name you call it, a new strategic era seems to be emerging. And for many, this new age holds out one distinct promise: the return of the United Nations to a principle role at the centre of international affairs. After all, what could be more natural, even necessary: a world weary of war turning once again to the pre-eminent multilateral institution for providing global solutions to global problems?

I know, it sounds great. In fact, I used to believe this, first as a UN political officer in Bosnia in the aftermath of the war, and subsequently at the organisation’s headquarters in New York, where I served for seven years as a special assistant to UN secretary-general Kofi Annan (a man whose qualities of leadership and patient diplomacy, in retrospect, served to mask the underlying decay of the institution he sought to lead toward a new identity as defender of individuals rather than states).

The reality, however, is that the UN – in its current, unreconstructed form – is the answer to yesterday’s question, the solution to problems of times past. To keep up with – much less lead – the dynamic political agenda in a fragmented and fractious 21st century, climbing back into a 60-year-old car simply won’t do.

The ground beneath the UN’s feet is not only shifting, it is cracking. And located right on the faultline of a fragmenting world, the organisation appears to be the first casualty among a number of 20th-century institutions out of step with a splintered landscape.

There is no need to belabour here the various, and vastly over-reported, ills of bureaucracy, inertia, corruption and incompetence from which the organisation suffers (not least since they pale into insignificance compared to practices in most of its member states, including some of its most powerful). That is not where the UN’s fate is sealed.

Nor is it merely a matter of the current secretary-general, Ban Ki-moon, appearing to many at the organisation to be more focused on ensuring the correct pronunciation of his name by the senior staff of the Secretariat than in taking a moral leadership role in confronting the atrocities that are taking place in Darfur. And despite what he has maintained, the suffering of the Darfuris is not caused by climate change. Janjaweed is not another word for thunder.

Least of all is this a matter of confirming the prejudices of the UN’s enemies on the political right. For them, let us be clear, the UN is an object of scorn mostly for its (in fact quite feeble) ability to challenge the unchecked use of power by states they consider friends or allies – democratic or not. A UN that would actually be effective in pursuit of its founding ideals is the last thing they want.

Devoted multilateralists like to say that if the UN didn’t exist we would have to invent it. But in an era defined by the diffusion of power of every kind – political, economic, ideological and ethnic – who is the “we” that would invent the UN today? This is the crux of the problem facing the United Nations and must be addressed with new instruments of order and progress – as often private as public, local as global.

One solution to the UN’s disconnect would be to abandon the dysfunctional theatre of the Security Council and the General Assembly, and reconstitute United Nations agencies that have demonstrated a consistent capacity to deliver on its founding ideals: agencies such as the High Commissioner for Refugees, the United Nations Development Programme and the World Food Programme. It is doubtful that even that would suffice as a response to the altered universe of decentralised power unfolding today.

A range of second-tier powers including Brazil, India, Iran, South Africa and Malaysia are joining the challenge posed by Russia and China to the strategic dominance of the United States, creating new alliances of interests. A ­de-coupling world economy of multiple market models is seeing the rise of new financial centres and trade blocs, even as sovereign wealth funds from Asia and the Gulf have increased their global influence at a time of financial distress in the West. And across the world we are seeing a sharpening of ethnic identities leading to nationalist demands for recognition and self-rule.

This is an emerging world of parts, of states drifting ever further away from each other into a global archipelago of interests and values with only the most severe common challenges summoning limited, and brief, periods of global cooperation. And even here, as the experience with undisputedly universal threats such as climate change or terrorism would suggest, what successes have been achieved owe more to discrete, separate, often ­regional alliances, and less to anything created through the UN framework.

The rise of global NGOs, militias, investment funds and private corporations – all with unprecedented power in the international order – makes a mockery of attempts to direct the course of global events from the headquarters of an institution whose membership is made up of nation states often represented by unelected leaders.

Historians of the future will record that in early 2008, a country in Africa faced a crisis of governance that unleashed long-dormant ethnic grievances and threatened a new genocide on the scale of Rwanda. They will note that the lone superpower, the great ex-colonial powers, the African Union, the UN and the EU all failed to persuade the parties to compromise. And they will be struck by the critical peacemaking role played by one man, acting alone – with only his reputation, temperament and diplomatic skill to aid him.

Kofi Annan succeeded in bringing Kenya back from the brink not despite the fact that he was out of office as UN secretary-general, but, arguably, because of it. What I think of as an archipelago world witnessed the first instance of the new diplomacy – divorced from traditional state interests, nimble enough to deploy political, economic and cultural tools in both public and private arenas.

A solution as complex and multi-faceted as the problem it confronted, and one that worked. It is surely a sign of the world to come.

1. Recognise evil: in the 1990s the UN was damaged by its inability to distinguish victim from perpetrator. 2. Ends not means: multilateralism has become an end in itself. Restore the focus on the great ends for which the UN was founded. 3. Conflicts: where major powers’ vital interests are at stake, it is futile for the UN to seek a leadership role. Focus on conflicts such as Burma and Zimbabwe. 4. Champion the rights of individuals: deny the worst abusers of human rights the chance to use principles of sovereignty as a licence to kill. 5. Adapt: devolve power to the UN’s agencies and programmes.