More than 180 world leaders will convene tomorrow to discuss problems of poverty, security, and global governance. The cynics have already pronounced the meeting just another talking shop signifying nothing. The cynics are wrong. Slowly, fitfully, the voices of the world's poor are breaking through the protective shield of the rich and mighty. Two weeks ago, a haughty US government was blustering. Today it is reeling from the plain sight of its own poor washed up in the floods of neglect.

The world leaders are at the United Nations first and foremost to discuss the Millennium Development Goals, five years after they were adopted and with a decade left to go to achieve them. Two weeks ago the US claimed that these international goals to fight poverty, disease and hunger did not even exist and tried to expunge the very phrase from the draft declaration of the summit. The rest of the world said otherwise: 190 countries told the US to back down, which it has done.

The goals are far from perfect. Critics have complained that the targets cannot even be measured precisely, much less achieved. There are indeed real problems of measurement. But why should we expect the rich countries to finance precise measurements of malaria when they won't spend just Dollars 3 per inhabitant of the developed world (Dollars 3bn, Euros 2.4bn, Pounds 1.6bn in total) to prevent and treat malaria, and thereby save more than 1m Africans per year?

Still, the targets have survived the cynics' attempt to expunge them because they have met a far more demanding test. They have caught the imagination of the world's poor, by demanding the world's attention to the fact that around 1bn of the world's poorest people lack access to the most basic needs of food, healthcare, safe shelter and clean drinking water. As many as 10m die each year as a result of being too poor to stay alive. The globally agreed targets have become their rallying cry.

The goals can be met. Scientists and engineers have shown clearly, convincingly and repeatedly how Africa can have its Green Revolution to end famines and triple food yields; how malaria, TB, and Aids can be brought under control; how electricity, connectivity and transport can reach even the most remote villages with the poorest people, at amazingly low cost. The sceptics ask why, if it's so easy, the goals are not being accomplished.

The answer is found in New Orleans. The poor are politically invisible. They die of neglect. And too many politicians are divorced from the most basic facts of science and engineering. The president of the US made clear last week that he had not been aware of the notorious vulnerability of New Orleans to a hurricane, even though the risk of such a disaster had been discussed in detail for decades. It's not entirely surprising. President George W. Bush also rejects climate science and Darwinian evolution.

The results of the summit still hang in the balance. The US government is pushing for many well-needed changes in UN organisation and management, but is also gravely weakening its case by insisting that the US should not be held accountable for foreign aid and specific progress against poverty.

The US is back-peddling on the commitment that donor governments made at the 2002 Monterrey summit "to make concrete efforts towards the target of 0.7 per cent of GNP" as official development assistance. It has even fought to eliminate language in the draft declaration calling for specific "quick wins" over malaria and other quickly achievable goals, to the deep consternation of the rest of the world.

With the US now receiving post-hurricane assistance from Europe, Mexico, and UN agencies, perhaps the US leadership will reflect more deeply on the meaning of real security in the 21st century, and thereby reach a consensus with the world's poor.

Secretary-general Kofi Annan was surely correct when he declared earlier this year that "we will not enjoy security without development, we will not enjoy development without security".

That is a valid lesson for the richest as well as the poorest countries on the planet.

Professor Jeffrey D. Sachs is director of the Earth Institute at Columbia University