Annan noted that HIV/AIDS is now disproportionately affecting women and girls.
Annan also declared that HIV/AIDS has been the single greatest setback to human development in history and is the greatest challenge that this generation faces.
The response to HIV/AIDS has begun to gain strength, Annan said, but he noted that last year more people died of AIDS than ever before.
Annan was speaking on the closing day of a UN General Assembly meeting that is due adopt a political declaration setting out a policy course aimed at ensuring that by 2010 everyone has access to treatment for HIV/AIDS.
The UN chief said that "radical change" is needed if the world is to "get anywhere close to universal access of HIV prevention, treatment and care and support by 2010."
For that to happen "requires real positive change that will give more power and confidence to women and girls, and transform relations between women and men at all levels of society."