This week Afghanistan's President has asked the world for $50 billion. It has not yet given its answer, beyond a sharp, sceptical yelp that the country could actually absorb funds on that scale.

But the subtext to Hamid Karzai's demand should really be: if you want me re-elected as President in next year's elections, then the price is $50 billion. For want of better alternatives, the West's choice is indeed going to be Karzai.

While other governments might accept that he needs some flashy achievements to brandish at home, they have no need to agree to this total and should demand that he gives a much better account of how he plans to spend any cash. Karzai, an embattled figure whose willingness to work with other governments has been patchy in the past year, has two justified complaints. First, donors have not delivered their pledges in full. Since 2001 countries have pledged $25 billion in help but delivered only $15 billion, according to a report by the Agency Co-ordinating Body for Afghan Relief, an alliance of 94 international aid agencies. Of the aid which did arrive, 40 per cent, or $6 billion, benefited donor countries through corporate profits and consultant salaries.

It is also impossible to argue with Karzai's point that the aid is desperately needed, both to lift one of the world's poorest countries a little farther from deep poverty, and to make any progress in defeating militants and eradicating opium poppies. More than a third of Afghans live below the poverty line; some estimates say 42 per cent. Healthcare has been one of the main targets of aid in the six years since the fall of the Taleban, but Afghanistan still has the world's second-highest maternal mortality rate, equal to Niger's, and better only than Sierra Leone's.

An energetic “hearts and minds” campaign to build the roads and water plants that people in the south particularly want is now at the centre of the British and American drive to bring the region under control. Military officers have been saying for two years that even though they can meet any military objective, real progress depends on politics, and that is going to need more local support. Hence the new focus (in theory) on building things, although measureable progress has been slight.

But Karzai still has to explain what he wants to do with the money. Here, he falls short, although the document that his officials will present to the donors' conference in Paris on June 12 is an incoherent 500 pages long: an exercise both myopic and grandiose that gives nation-building an even worse name than it has already. At least $14 billion is to be spent on improving security. Unfortunately, this is all too plausible. As Iraq has shown, security can absorb almost limitless amounts of cash. Getting real development projects started would take far more security than now, to protect the people working on them, and to protect the construction from attack once it is complete.

But what does Karzai mean by security? International forces have reached their limit. More Afghan ones? Karzai intends to keep expanding the Afghan Army and police, but surely this should be stated as a goal in itself.

And the rest of the budget? The key target is reviving the decrepit agricultural sector, Ishaq Nadiri, senior economic adviser to Karzai, said on Tuesday. Again, this is a plan on which the Afghan Government and outside advisers entirely agree. Persuading farmers that they can make a livelihood from farming, in a country that used to be renowned for its fruit, is one of the few good plans for trying to undermine the opium business. This is a rare case of a problem that is made easier by the rise in food prices.

But here, Karzai's demands ring hollow. It is not credible that Afghanistan's farming can absorb these sums so quickly. More likely, pouring cash into areas under the control of opium barons will give them another stream of income.

Karzai deserves support for what is a blunt political threat: he needs help, in the form of visible trophies, to get re-elected, and for all his huge faults as the West's partner, he is the best choice going. That doesn't mean he deserves $50 billion.

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