A lack of funds prevents children being tested for the virus

The fund should have the backing of the world's richest countries, but, at the same time, rich countries should not simply throw money at the problem without a proper structure in place, he said.

And the poorer countries should have a responsibility, too, Professor Sachs told the BBC.

"My belief is this could be done and I think we should be selective - that countries really have to do their part to make this money worthwhile," he said.

"My view is that if we pooled the resources, had a major global effort, put a lot of expertise into it and a lot of monitoring and financial auditing, you could keep a lot of the abuse really down to much lower levels than truly has been typical of just handing over money."

Professor Sachs estimated that at least $4bn a year was needed to pay for the prevention and treatment of the disease, and to care for Aids orphans. In several years that figure would probably rise to $7bn or $8bn a year, he said.

Current spending on Aids in developing countries totals about $1bn. Mr Annan said between $7bn and $10bn was needed.

Tackling attitudes

The fight against the virus received a boost last week when 39 pharmaceutical companies contesting a South African law that could provide cheaper versions of branded Aids drugs unconditionally dropped their case.

We need to make people responsible

Obed Qulo, Aids Foundation of South Africa

It cleared the way for government plans to import or manufacture the cheaper drugs.

But education and support are also crucial to tackling HIV and Aids, the Aids Foundation of South Africa told BBC News Online.

One of the real problems was getting the message through to people in war-ravaged nations, said spokesman Obed Qulo.

"People say to us, 'What is the point worrying about HIV/Aids if I can get killed tomorrow?'."

And the key to prevention was "a step beyond education", he said. You could inform people about the existence of the virus but it was another thing trying to get them to use condoms.

'Medical experts'

Kofi Annan's proposed global fund should be about countries pooling their money and submitting proposals as to how the money should be used, suggested Professor Sachs.

"Those plans would be reviewed, really by the medical and public health experts for a change," he said, "and if approved, then monitor-able programmes would gain access to these grant funds."

Kofi Annan wants to change social attitudes

"There's no question that the rich countries - the US, Canada, Europe, Japan - have to take a completely different view of global health.

"And the country that needs to come first in doing it differently is the United States, because the US has been so grossly under-performing in term of the level of assistance that it gives to the rest of the world, especially to the poor countries."