The World Health Organization says male circumcision reduces the risk of female-to-male transmission of the disease by around 60 percent. But only 30 percent of men worldwide have had the procedure, mostly in countries where it is common for religious or health reasons.

Bailey told a major international AIDS conference in Sydney, Australia, that world health agencies should be aggressive in implementing the procedure in light of mounting evidence of its effectiveness in preventing new HIV infections.

Circumcision, the removal of the foreskin from the penis, has long been suspected of reducing men's susceptibility to HIV infection because the skin cells in the foreskin are especially vulnerable to the virus.