Male circumcision could prevent millions of HIV infections every year and play a major role in controlling the virus' spread in developing nations, a major AIDS conference was told Tuesday.

US researcher Richard Bailey called on health authorities to actively promote circumcision, saying the scientific evidence left no doubt that it could reduce HIV infection rates by up to 60 percent.

Bailey, from the University of Illinois, said three studies in Africa had all confirmed a long-standing belief about the effectiveness of circumcision in reducing the risk of HIV infection.

"The last two were actually stopped early because they showed such a high level of efficacy that it wouldn't be ethical to continue the trial and withhold circumcision from the control group," Bailey told reporters at the International AIDS Society conference in Sydney.

He said universal circumcision could avert two million new infections and 300,000 deaths in sub-Saharan Africa over 10 years.

Bailey said while health authorities would rush to implement a vaccine that was 60 percent effective, there was an element of squeamishness in some cultures about promoting male circumcision.

"It's been a really long haul because it's the penis after all, so it's not that easy to accept that kind of intervention," he said.

"Circumcision is not just simply a medical procedure, it's tied up in a complex web of cultural and religious practices and beliefs, so it's not easy for politicians and ministries of health to very quickly come out in favour of circumcision in countries where it's not traditionally practiced."

Bailey said leaders in developing nations needed to endorse circumcision because international health authorities would not impose it because they feared being seen as culturally insensitive.

"But the time to act is right now," he said. "Delaying the roll-out of circumcision could be causing more harm, not just because more people are getting infected with HIV than necessary but also people are going to unqualified practitioners."

The conference also heard that the practice, common in Africa, of women rinsing themselves with lemon juice after sex did not reduce the risk of HIV infection.

Nigerian researcher Atiene Sagay said a study of more than 300 Nigerian prostitutes found that women douched to avoid infection but it was totally ineffective.

"People suggested it could be a microbicide (but) we know much better than that now," Sagay said.

He said the practice was not an effective contraceptive measure either, as alkaline semen easily neutralised citric acid.