Caribbean countries say six leading pharmaceutical companies have agreed to supply them with anti-Aids drugs at huge discounts.

Companies involved

GlaxoSmithKline Hoffman-La Roche Boehringer Ingelheim Bristol-Myers Squibb Co Merck and Co Abbott Laboratories

Guyana's Health Minister, Leslie Ramsammy described the deal as a "major victory for us as a region," the Associated Press news agency reports.

However, Aids campaigners warn that the drugs will still be too expensive for many in the region.

The deal is expected to be signed at the 14th International Aids Conference which opens in the Spanish city of Barcelona on Sunday.

'Coup'

The six companies will reduce the price of the drugs to the 15 countries in the Caribbean Community by up to 90%, the Prime Minister of St Kitts and Nevis, Denzil Douglas said.

He estimates that at least two-thirds of Caribbeans infected with the HIV cannot afford drugs treatments at present.

Guyana Leslie Ramsammy told Reuters news agency: "The drugs become affordable and the Caribbean can begin universal treatment."

"It's a major coup for us."

He said most Caribbean countries would benefit from the deal.

However, some observers say that, with poverty rife in the region, the discounts may have limited impact.

Resistant drugs

The Barcelona conference opens in the shadow of a report showing that HIV drugs may be losing their effectiveness.

A study in the Journal of the American Medical Association has found that one in four new cases of HIV infection in San Francisco are resistant to some classes of antiretroviral drugs.

Researchers from the Gladstone Institute of Virology and Immunology said the finding highlighted the need for new classes of drugs to be developed.

Experts hope the Barcelona Aids conference will kick start efforts to stop 68 million people dying from the disease by 2020.

Top of the agenda will be last week's report by UNAids suggesting the epidemic is still in its early stages and is spreading fast.

Conferences like this one are always a major opportunity to draw attention to Aids throughout the world

Dr Peter Piot, UNAids

It will also hear calls for the richer countries to do more to help the developing world to tackle the disease.

Delegates will also be told of plans to launch the world's largest HIV vaccine trial involving 16,000 people in Thailand.

Dr Peter Piot, UNAids executive director, told BBC News Online he hoped the conference will serve to focus minds on what needs to be done.

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"My hope is that participants will go home with a sense of what they have got to do in their environment and those coming from wealthy countries will hopefully also devote some time and energy to solving problems in poor countries," he said.

The World Health Organisation estimates that $10bn is needed annually to fight Aids. At present, just $3bn is spent.