You'll think I'm off my trolley, Bob Geldof said this week. And indeed the aid agencies did. The Bush administration has the most positive approach to Africa of any United States government since Kennedy, Geldof said. Nonsense, the aid boffins replied.

So who was right? There can be no doubt that President George Bush's recent pledge of $15bn of new money to fight HIV and Aids in poor countries is significant. And it seems churlish to point out that ­ in deference to right-wing US Christians ­ a third of the prevention money is to be tied to campaigns promoting sexual abstinence. It's a lot of money, even if it is, as a proportion of GDP, less than Uganda gives to the global Aids fund.

But does it outweigh America's veto of the move to provide cheap anti-Aids drugs to the Third World? At the World Trade Organisation ministerial meeting in Doha, Qatar, in December 2001, the rich nations agreed that poor countries, such as Ethiopia, could waive patent rights for drugs to fight public health emergencies. The trouble is that America has the most restrictive interpretation of the agreement. Washington insists poor countries have to apply to the WTO for a waiver in each individual case, but most of them can't afford to fight the might of the US government and drug giants such as GlaxoSmithKline. During the US anthrax scare, in which two Americans died, Mr Bush forced Bayer, which makes an antidote, to halve its price, but when it comes to a conflict of interest between 28 million Africans who are HIV positive and US pharmaceutical profits it's clear where he comes down.

Geldof is right in saying the US has outstripped the European Union in donations to Ethiopia. But US food aid is often American grain surpluses, produced under subsidy, which is why when world prices go down, US food aid goes up. It rarely buys food aid on African markets.

Moreover, the declared strategic aim of the food aid policy is to "expand commercial markets". The US identifies a market ­ Nigeria, Peru, Taiwan, Colombia, South Korea and Indonesia have all been addressed ­ and swamps the market with cheap grain, driving prices down, bankrupting local farmers and creating a captive market. This explains why more food aid goes to the Philippines than to the whole of the starvation-prone Horn of Africa. The US creates conditions for hunger with one part of its food-aid programme and gives a bit of humanitarian relief with another.

Then there is trade. The Africa Growth and Opportunity Act (passed by Bill Clinton, implemented by George Bush) is supposed to be a series of trade preferences for Africa ­ in textiles and oil. To qualify, Third World countries have to import their yarn from the US. They also have to agree to enforce US intellectual property law. It is an unequal arrangement that even the IMF says costs Africa more than $500m (£300m) a year.

Finally comes dumping of US products produced under subsidy. George Bush has underwritten one of the biggest expansions in the history of the US farm subsidy programme. The $400m he pours each year into the rich US cotton belt wipes out the livelihood of millions of small cotton farmers in Africa.

A row is rumbling between America and France, which has proposed a moratorium on dumping. There are mixed motives ­ French investment in the African cotton sector is being wiped out because of US dumping ­ but Oxfam has praised the plan. The French propose the EU should curb subsidies and America should limit the $8bn a year it spends on export credits ­ two techniques to achieve the same end of subsidising Western farmers at the expense of Africans. Mr Bush, with Tony Blair's post-Iraq anti-France backing, has said no way.

So Bob, when it comes to choosing between the poor in Africa and US vested interests, I'm afraid there's little question whose side George W Bush is on.