The World Health Organization says there are enough HIV drugs available despite four in five failing quality tests.
Too few have access to cheap drugs
It has set a target of getting antiretrovirals (ARVs) to 3m in the developing world by the end of 2005.
Only 440,000 of the 6m people who need these drugs are now receiving them.
Speaking on World Aids Day, the WHO said that some cheaper non-brand drugs had not passed international standards, but there were enough to meet demand.
Although they are not a cure, ARVs block the virus's ability to replicate.
They can delay the onset of Aids by slowing the attack on the immune system.
WHO set up a scheme to certify the quality of HIV drugs, including generic versions, to guide buying by
Generic drugs are the same as brand-name products, but are dispensed under its generic chemical name.
They are cheaper, and can be sold on the market when the patent has expired on the branded version.
WHO says generic versions have to be proved to be of equivalent quality as the patented drugs.
Their standards are more stringent than those applied by many countries.
This has meant many drugs have been excluded from the WHO list.
The organisation said 13 medicines had been voluntarily withdrawn from its list, which contains about 30 different generic Aids treatments, so they too could be re-evaluated.
Dr Lembit Rago, WHO coordinator for essential medicines and drugs, said: "It could be seen as a short term pain but I think it will be outweighed by a long term gain."
Two generics by the Indian drug maker Cipla for treating HIV/AIDS have been reinstated on the WHO list six months after being removed.
Lamivudine, and lamivudine combined with zidovudine,
were returned to the list after fresh inspections proved they were bioequivalent to their patented counterparts.
WHO officials said they hoped news of the reinstated drugs would encourage other producers to speed up the re-testing process of 16 other de-listed HIV drugs.
Dr Jim Kim, director of WHO's HIV/Aids department, said: "We know that access to essential medicines is a critical part of our efforts to scale up treatment
for people living with HIV.
39.4 million people are living with HIV globally, up from an estimated 36.6 million in 2002
Nearly half of the adults living with HIV are women
The most rapid spread of infection has been in North Africa and the Middle East
Source: UNAids estimates 2004
"The efforts of both our own department and the generic
manufacturers to get these drugs back on the list is an extremely encouraging development."
MSF currently provides antiretroviral treatment to more than 23,000 people living with HIV/AIDS in 27 countries in Asia, Africa, Latin America and Eastern Europe.
Dr Rowan Gillies, president of MSF International, said: "MSF has succeeded in making a difference to our patients and their families, but we have not seen massive scale-up efforts in most of the countries we work in.
"Outside the few clinics offering ARVs, the treatment landscape is a desert.
"The imperative to fund and manage treatment programmes is still being neglected."
He said more money should be put behind WHO's drug quality checks.
"There's no way we can deal with the problem without generic drugs," he said.
"WHO announced its target this time last year and we have not got anywhere near it, and it's 2005 next month.
"There are still these five or so million people who will die in two years if they do not get the drugs they need."
He said one of the main obstacles was a lack of trained medical staff in the developing world to treat people with HIV and Aids.