GENEVA - The United Nations on Wednesday endorsed male circumcision as a way to prevent HIV infections in heterosexual men and said it should be made more easily available in African countries.

Two U.N. agencies, the World Health Organisation (WHO) and UNAIDS, backed recent research showing that removing the foreskin of the penis can more than halve men's vulnerability to the virus causing AIDS from having sex with HIV-infected women.

They said that countries with high rates of heterosexual HIV should urgently improve access to male circumcision, giving priority to sexually active young men, while continuing to promote condom use and encourage regular testing.

"These recommendations represent a significant step forward in HIV prevention," said Kevin de Cock, the WHO's director for HIV/AIDS programmes, pointing to big potential gains in places where male circumcision is rarely practised.

"Scaling up male circumcision in such countries will result in immediate benefit to individuals. However, it will be a number of years before we can expect to see an impact on the epidemic," he said.

Of the 40 million people worldwide infected with the human immunodeficiency virus, 25 million live in sub-Saharan Africa, where the disease is spread mostly through heterosexual sex.

The WHO and UNAIDS said increasing male circumcisions could prevent 5.7 million sub-Saharan African men from contracting HIV over the next two decades, and save 3 million lives.

Some 30 percent of men worldwide are currently circumcised. The practice occurs for religious reasons among Jews and Muslims and in others for hygiene purposes, generally among infant boys.

Researchers have previously noticed that HIV tends to be less prevalent in areas where circumcision is common, and three large African studies have in past months found that circumcised men are 50 to 60 percent less likely to catch the AIDS virus.

Experts believe cells on the inside of the foreskin, the part of the penis cut off in circumcision, are particularly susceptible to HIV infection.

There is no evidence that women are any more protected from HIV when they have sex with circumcised men, though research in that area is ongoing, WHO and UNAIDS officials said.

If male circumcision results in an overall decrease in HIV infections then women would eventually benefit, they said.

Studies undertaken so far indicate little benefit from male circumcision for men who have sex with other men.

It is up to each individual country to decide how to improve their male circumcision access, the U.N. agencies said, estimating the procedure would cost $50 to $100 per person.

"In view of the large potential public health benefit of expanding male circumcision services, countries should ... consider providing the services free of charge or at the lowest possible cost," they said in a joint statement.