More than 10,000 medical experts are expected to attend the conference in the coastal town of Durban.

The protest organisers aim to present the conference with a list of demands to ensure that drugs for people infected with the HIV virus that causes Aids are made available at affordable prices.

The protesters, a coalition of local Aids groups called South Africa's Treatment Campaign (TAC), say they ready to disrupt the conference to help secure change.

Demands

"We are not in Africa, amongst the death and destruction caused by HIV for extravagant cocktail parties feted by drug companies. We expect change. We expect a plan for affordable medicines," the statement said.

Mbeki: clarification of his views is eagerly awaited

Recently, five major pharmaceutical companies offered to slash the price of anti-Aids drugs from $16 to $2 dollars for a daily dosage.

But activists say that is still too expensive.

They plan to ask the UN and the Southern African Development Community, SADC, to ensure affordable medicines for HIV patients by December.

Mbeki's views

They will also be watching closely the speech made by President Thabo Mbeki, who is due to open the conference.

President Mbeki has previously said that the link between HIV and Aids is not proven -- a stand criticised as inaccurate and irresponsible by mainstream scientists.

AZT pills could save many children from infection

As a results of his views, Mr Mbeki appointed a panel of international and local scientists to advise the government on its policy towards Aids - a body which includes scientists who also question HIV's role.

After receiving advice from this panel, Mr Mbeki is expected to use his speech to clarify his views - which are vitally important in view of the high prevalence of HIV and Aids in South Africa.

The United Nations estimates that there about 4.2 million Aids sufferers in South Africa, with 1,500 more people infected every day.

Pregnant women

The UN also says that 22% of pregnant women in South Africa are HIV positive.

But the South African Government refuses to make the drug AZT available to them, although it is believed to curtail the rate of infection from mother to baby.

The protesters say that that too must change.

The head of the HIV/AIDS Research Unit at South Africa's Medical Research Council, Dr. Salim Abdool-Karim told Reuters: "There are no major medical breakthroughs."

He said the delegates would simply hear what they already suspected: that AIDS was spreading at astonishing rates in the developing world and would keep on spreading for the next few years, no matter what anyone did.