Foreskin cells are thought to be more vulnerable to HIV infection

The World Health Organization and UNAIDS said circumcision should be added to current interventions to reduce the spread of HIV.

Three African trials have shown that circumcision halved the rate of HIV infection in heterosexual men.

The recommendations largely apply to countries where rates of heterosexual transmission is high.

Experts warned that greater use of circumcision would not replace the need for other prevention methods, such as condoms.

But modelling studies have shown that if male circumcision was more widely available, millions of lives, particularly in sub-Saharan Africa would be saved.

WHO and UNAIDS said access to the procedure should be urgently scaled up in areas with high rates of heterosexual infection and low rates of male circumcision.

But warned that it was an additional intervention and would not replace programmes providing HIV testing, or prevention or treatment for sexually infected infections.

Men and their partners must also be given counselling to prevent them developing a false sense of security, they said.

Training and monitoring must be done to check circumcision is being done by appropriate health professionals in a sanitary environment with proper equipment.

And they stressed there was no evidence yet as to whether circumcision has any impact on the risk of infection for the woman or on the risk among men who have sex with other men.

Significant step

Kevin De Cock, director of HIV/AIDS at the World Health Organization said: "The recommendations represent a significant step forward in HIV prevention."

"Countries with high rates of heterosexual HIV infection and low rates of male circumcision now have an additional intervention which can reduce the risk of HIV infection in heterosexual men."

However, he said it would be years before the impact on the epidemic would be apparent.

Catherine Hankins, UNAIDS, said: "Being able to recommend an additional HIV prevention method is a significant step towards getting ahead of this epidemic.

"However, we must be clear: male circumcision does not provide complete protection against HIV.

"Men and women who consider male circumcision as an HIV preventive method must continue to use other forms of protection such as male and female condoms, delaying sexual debut and reducing the number of sexual partners."

All three African trials were stopped early because the results were so dramatic - with reduced rates of new HIV infections of 48-60%.

There are several reasons why circumcision may protect against HIV infection.

Specific cells in the foreskin may be potential targets for HIV infection and also the skin under the foreskin becomes less sensitive and is less likely to bleed reducing risk of infection following circumcision.

When Aids first began to emerge in Africa, researchers noted that men who were circumcised seemed to be less at risk of infection but it was unclear whether this was due to differences in sexual behaviour.

Deborah Jack, chief executive of the National AIDS Trust, said: "These recommendations address many of the benefits of including male circumcision in a comprehensive HIV prevention package.

She added: "Additional research to determine the health impact for women and men who have sex with men is vital, as is ensuring that adequate resources are provided to fund existing prevention methods, as well as continue research into new technologies such as microbicides and vaccines."