On 20 September, the largest assembly of world leaders since the Millennium Summit of 2000 gathered at the United Nations in New York for the tenth anniversary of the adoption of the Millennium Development Goals (MDGs), a globally agreed set of targets to halve world poverty by 2015. However, the summit was neither commemoration nor celebration, but more of an emergency revival meeting. The financial crisis could have made it an autopsy, but the UN secretary general, Ban Ki-moon, backed by Gordon Brown, ensured that the G20 meeting in 2009 kept the MDGs on the agenda. These meetings were about keeping them on track.

From the beginning of his term in office, in 2007, Ban made the MDGs and climate change signature issues. He worked hard to ensure an influential turnout for this General Assembly, lobbying governments across the globe to attend. But ostentatious do-gooding is not in the quiet style of the former South Korean foreign minister. Indeed, his focus on internal diplomacy with heads of state has caused him to neglect some of the public diplomacy opportunities offered by his current position.

Ban's youthful ambition in Korea was always to be a diplomat, he told me when we met at his UN office this year. "In 1962, when I was a third-grade senior in high school, I came to the US as an exchange student, brought by the American Red Cross, and met President John F Kennedy at the White House. It was a most inspirational experience as a very young boy from a very poor country, destroyed by the Korean war. I thought, what should I do for my country, totally devastated by war? I thought I could contribute by being a diplomat, and helping enhance the status and prestige of Korea."

His appreciation for the organisation dates from the same era: "The UN has been and continues to be a beacon of hope to Koreans. It was the UN which really saved us - 16 countries came to the aid of Korea when North Korea attacked. It was the first enforcement action under the UN Charter, after only five years!"

Ban, approachable when he interacts with the UN press corps, originally ducked a high media profile. His modus operandi has been to make explicit statements of the UN's position on specific questions, but to refrain from direct public criticisms of national leaders. Yet he told me that his meetings with leaders "have been quite straightforward and very vocal . . . Most of my senior advisers were quite surprised by how outspoken I was."

Simmering sentiment

His diplomatic style, however, is more umpire than player. He says, "The secretary general is not a negotiator. The members do the negotiation; we provide and facilitate . . . it is the member states which have to negotiate, which have to agree." That was about climate change, but since the MDGs were entrusted to the UN, his team has been retargeting them, in the hope of concentrating members' attention on the most cost-effective goals: technology, education, women, small farmers and global health, particularly that of women and children, as maternal and infant mortality are among the most visibly failing MDGs. As Ban said ahead of the meetings: "No area has more potential to set off a ripple effect - a virtuous cycle - across the goals than women's health and empowerment."

But his efforts have not been helped by recent attacks from international diplomats, echoed by the press. In August 2009, a letter was leaked to the press from one of Norway's ambassadors to the UN, condemning the secretary general's "absence" and passivity in the face of critical crises such as those in Burma or Somalia. At the same time, the neoconservative writer Jacob Heilbrunn published an article in the journal Foreign Policy describing him as a "nowhere man" and "general nonentity". Anti-UN sentiment in the US is always simmering; as a result of these attacks, Ban's aides have realised how vulnerable his low profile and his tendency only to react to events have left him.

Yet Ban has been more outspoken on international matters than expected. Many liberal UN supporters had low expectations of him when he started, given that he was a nominee of the Bush administration and seemingly a protégé of the arch-conservative John Bolton (acting US ambassador to the UN from 2005-2006). But during the hustings for secretary general he expressed unequivocal support for the International Criminal Court, against which Bolton had fought obsessively, and for the Responsibility to Protect initiative. His position, he says, came from his time as foreign minister when he visited the massacre memorial in Rwanda. "I was so saddened and horrified by what I saw there. I was convinced the international community had to take steps to prevent anything like what had happened."

On the Middle East, his statements have been considerably more explicit than those of his immediate predecessor, Kofi Annan. With limited experience of the region before office, he initially adopted a position that was reflexively pro-Israeli. But greater exposure to the intricate details has clearly been educational, and his recent statements on Gaza and the aid flotilla protest stand in contrast to the tactful silence of most western leaders. When Israel insulted Vice-President Joe Biden by announcing new settlement-building during Biden's visit to Tel Aviv in March, Ban reiterated "that settlements are illegal under international law". He also scored a first for the UN by securing $10.5m from Tel Aviv by way of compensation for the UN premises in Gaza that Israel destroyed during Operation Cast Lead.

Hue and cry

“My dialogues with Israel and Arab governments have always been based on my convictions, human rights and resolution of differences of opinions - and in that regard I have had trust from both parts," he told me. "Of course my dialogue with the Israelis has been quite difficult," he conceded, but despite the challenges he has kept open channels of communication.

Luckily for Ban, he has not had the difficulties that Annan faced, of confronting warmongering pressure from the US and the UK as they moved towards the invasion of Iraq in March 2003. The Obama administration has also been more amenable and not followed the Democratic line, set by Bill Clinton and Madeleine Albright, of browbeating the UN and the secretary general into submission - never mind the outright hostility of George W Bush.

That might not last. With the MDGs needing cash from the world powers, and the prospect of a Republican majority in Congress after the midterm elections in November, it is likely that the usual American hue and cry against the UN and its leader will begin again. This would only be amplified by a sense of betrayal that "our" nominee appears to believe in the institution as an active force for international progress. Ban would benefit from engaging in further high-profile diplomacy to let the world know that this is exactly what he believes.

Ian Williams is the author of "The UN for Beginners" (Writers and Readers, £6.99)

How to save 16 million lives

Ten years on, progress towards achieving the Millennium Development Goals (MDGs) is not encouraging. The world leaders assembled in
New York for this month's summit heard that the eight commitments, which include pledges to eradicate extreme poverty and hunger and to combat HIV/Aids, will not be met by 2015 without considerably more investment and effort.

The largest gaps between commitment and reality are in child and maternal mortality. The MDGs pledge to reduce the under-five mortality rate by two-thirds between 1990 and 2015 and to reduce the number of maternal deaths by three-quarters over the same period.

Nick Clegg, representing the UK at the summit, announced that the UK would commit to doubling the number of lives of women and babies saved by 2015 through "reorientating" the government's aid programme. As well as ring-fencing the development aid budget, the coalition has promised to meet the UN target of raising aid levels to 0.7 per cent of gross national income by 2013.

The UN secretary general, Ban Ki-moon, also unveiled a strategy focused on women and children. It is estimated that the plan could save 16 million lives by 2015 by improving funding for maternal and infant care in developing countries.

Caroline Crampton