WHO officials said the pills, key to its ambitious goal of getting ARVs to the world's poor, were made by India's generic drugs firms Ranbaxy Laboratories and Cipla Ltd. and combined the drugs lamivudine, stavudine and nevirapine.

Making the announcement, WHO Assistant Director-General Jack Chow told a news conference that research was helping simplify Aids therapy and his organization now recommended just four treatment regimens, whereas previously it recommended 35.

Of the four, the most appropriate regimen for people living in deep poverty is so-called fixed-dose combination therapy that combines medicines in a pill that needs to be taken only twice a day, in the morning and evening, WHO experts say.

"The exciting development of single pills containing all three drugs will make treatment even simpler," Chow said.

"Today, we are pleased to announce that WHO has prequalified three preparations of this single pill three drug combination."

WHO officials said it was the first time WHO had approved the use of a three-in-one combination pill that was suitable for what WHO terms "front line" conditions of extreme poverty.

Prequalification means the WHO experts have visited and inspected the factories making the pills and satisfied themselves the product is safe, effective and of good quality.

WHO is not a global regulator of pharmaceutical production but its recommendations guide government policymakers around the world, and government purchasers feel confident buying products that have the WHO seal of approval.

The patents for lamivudine, stavudine and nevirapine are controlled by multinational drug companies GlaxoSmithKline Plc, Bristol-Myers Squibb Co and Boehringer Ingelheim, respectively.

To date the brand pharmaceutical companies have not co-operated to combine their medicines into a single pill; only generics companies offer fixed-dose combination anti-Aids pills seen as workable in settings of poverty, experts say.