No one should begrudge Helen Clark her success in becoming the Administrator of the United Nations Development Programme, the world body's third highest ranking position. In many ways, her political career, and particularly her interest in international relations, led unerringly to this. It represents a considerable achievement for not only the former Prime Minister but for this country and a Government that strongly supported her candidacy.

Equally, no one should be in any doubt about the difficulties that will confront Helen Clark in New York. The UNDP, the aid and development arm of the UN, operates in 166 countries with an emphasis on poverty reduction, democratic governance, crisis prevention and recovery, sustainable development and reducing environmental degradation. Most fundamentally, it is charged with being a prime player in delivering a pledge by world leaders, delivered at the UN Millennium Summit, to halve global poverty by 2015. Helen Clark comes to this job a little over halfway through this process, and at a time when global events threaten its very undoing, especially in Africa.

Her predecessor, Kemal Dervis, a former Turkish Finance Minister, has spent much time warning that the volatile economic situation is bound to affect global development efforts, and seeking to minimise the impact on the world's poorer nations. The UNDP's $9 billion budget is funded entirely by voluntary contributions from member nations. Many of them will, inevitably, be questioning whether their first spending priority should be to their own citizens.

Helen Clark will have to continue Mr Dervis' work in urging them not to lose sight of the global picture and the perils of increased poverty.

While the economic environment presents a daunting challenge, there are pluses to becoming a significant UN player at this time. Several years ago, the former Secretary-General, Kofi Annan, began a push for the body to be modernised to reflect the new world order more accurately. This would involve expanding the number of permanent members on the Security Council to include the likes of India, Japan, Germany, Brazil and one or two African nations. The initiative was effectively scuppered by President George W. Bush, who saw the UN as, variously, an irrelevance or a body to be subjugated.

Barack Obama, his successor in the White House, has a far different view of world affairs. His penchant for international co-operation augurs well for a more credible and involved UN. The British Prime Minister, Gordon Brown, a supporter of Helen Clark's candidacy, has picked up Mr Annan's baton. There will be increasing pressure on the Secretary-General, Ban Ki-Moon, whose appointment was much influenced by the Bush Administration, to orchestrate reform. The promise of a more relevant and realistic UN would enhance its profile, and go a long way towards convincing countries that maintaining the level of their contributions to the UNDP was worthwhile.

If this process is to be successful, Helen Clark must play a major role in her four years as head of the UNDP. Diplomacy, firmness and forcefulness will be required in equal measure. In her favour, there are plenty of examples of the impact that one person can make at the world body. A recent instance was Mary Robinson, the former President of Ireland, who was a hugely successful advocate as the UN High Commissioner for Human Rights. Helen Clark will, like her, have to take the UN message far and wide, as well as astutely addressing the profuse politicking in New York. Billions of the world's poorest people will hope she delivers as much as her record and resolve suggest she will.