The US government is threatening to obstruct low-income countries from accessing generic HIV/AIDS drugs approved by the World Health Organization, a human rights group charged on Friday.

The US, it said, is convening a conference in Botswana on Monday that may challenge WHO's approval of generic copies of patented AIDS drugs.

In a statement, the Human Rights Watch said the drugs in question meet the stringent standards of WHO's technical review for generic drugs but have not been approved by the US Food and Drug Administration.

The US, under pressure from pharmaceutical companies selling the brand-name equivalents, claims instead that "there are no uniform principles, guidelines or international standards addressing the development" of generic drugs- "an assertion that calls into question WHO's widely accepted review process," the US based Watch added.

"WHO has made enormous headway in verifying the quality of generic AIDS drugs that are the only hope for millions of low-income people with AIDS," said Joanne Csete, director of the HIV/AIDS Programme at Human Rights Watch.

"But to protect brand-name pharmaceutical interests, the United States may dash that hope."

The generic drugs opposed by the US, it stressed, allow people with HIV/AIDS to take only two pills a day, and they are much cheaper than the equivalent brand-name drugs.

The cheapest generic regimen, also endorsed by Doctors Without Borders and other health practitioners, costs $140 per year per patient as opposed to the brand-name equivalent of six pills a day costing at least $600 per year.

Numerous UN bodies, including the Commission on Human Rights, have recognised that access to affordable medicines for HIV/AIDS is essential to the right to health, the Watch said.

Generic drugs, it added, are an integral part of WHO's recently announced "3 by 5" initiative-a plan to ensure access to HIV/AIDS medicines for at least 3 million persons with AIDS by end-2005.

In spite of WHO's approval, Randall Tobias, the US Global AIDS Coordinator, told reporters that the United States is unsure that generic drugs meet the "principles and standards" necessary to qualify for US support for their use.

President George W Bush praised the development of cheaper AIDS drugs in his State of the Union Address in January 2003. But since then, the US government's "presidential emergency programme" on HIV/AIDS has not purchased or promoted the use of generic drugs.

"The United States stands alone in opposing these safe, inexpensive and WHO-certified generic medicines," said Csete.