The United Nations Population Fund said the number of people between the ages of 15 and 25 is the largest ever, with one billion people around the world entering their reproductive lives. However, two-thirds of all new HIV infections occur in that age group, prompting calls for better reproductive health care. The issue was discussed at the international AIDS conference in Barcelona.

The U.N. agency said the HIV/AIDS epidemic has caused "biological sexism." It said women's bodies are more susceptible to both HIV and other sexually transmitted diseases. In fact, men are eight times more likely to transmit HIV to women through unprotected sex, than women are to men.

As a result, the U.N. Population Fund said the average HIV infection rate in teenage girls is five times higher than in teenage boys. And among people in their 20s, the rates are three times higher in women than in men.

The agency's HIV/AIDS coordinator, Suman Mehta, said unprotected sex, rape, female genital cutting, forced marriage and the inheritance of widows among brothers puts women at risk.

"Roughly 47 percent of the 1,500 new infections every day are in women of child-bearing age. Women are biologically susceptible to HIV and other sexually transmitted infections. This is compounded, of course, by the social, cultural and economic circumstances that often make it difficult for women to have control over their lives," Mr. Mehta said.

Dr. Mehta said young women and men, especially those who are not married, often face barriers to prevention. She said stigma, embarrassment and timidity prevent them from visiting family planning clinics or other programs providing reproductive health care services.

Benjamin Raletsatsi, of Botswana's Family Welfare Association, counsels young people on health care. "I fear for the young people of Botswana and the world. In the time that I'll speak to you, 15 young people in the world will be infected with HIV. We must stop this clock and put an end to the needless dying of the young people," Mr. Raletsatsi said.

He said young people need to be educated about AIDS prevention, if they are to be the parents and leaders of tomorrow.

"The young people of my country will not grow up to see their grandchildren. Too many of us will die before we are 40. In order for our generation to grow old it is essential that we reach young people now," Mr. Raletsatsi said.

The U.N. Population Fund's campaign, "Saving Women's Lives," calls for an end to "the global crisis in the availability of reproductive health materials, particularly condoms and other contraception."

It also said pregnant women must be able to learn their HIV status and have priority in treatment. The U.N. Population Fund calls for educating boys to reject cultural practices that "subordinate and denigrate women or encourage risky sexual and drug using behavior."