New York: UN Secretary General Ban Ki-moon called for an end to the stigma associated with HIV/AIDS, saying it remains the biggest challenge in fighting the disease that has infected tens of millions of people.

World AIDS Day on December 1 each year brings together organisations that have been fighting the disease that has killed more than 25 million people since the 1980s.

The millions of people infected and living with the AIDS virus bear the stigma of the disease, Ban said on Friday.

"Overcoming stigma remains one of our biggest challenges," Ban said. "It is the single barrier to public action on AIDS. It is one of the reasons why the epidemic continues to wreak its devastation around the world."

He said HIV/AIDS is "unlike any other" disease because it is also a social and human rights issue, and an economic issue, targeting young adults at a time they can contribute to economic development, intellectual growth and childrearing.

The UN has called for halting the spread of the disease by 2015, but some countries have succeeded more than others in implementing national programmes in fighting AIDS.

"We have made tangible and remarkable progress on all these fronts," he said. "But we must do more."

"On World AIDS Day, let us show the leadership it takes to live up to our responsibility," Ban urged UN members.

The Unaids programme and World Health Organisation said in Geneva in November that more than 33 million people are currently living with HIV, the virus that causes AIDS, down 16 percent from last year's 39.5 million, after the two organisations revised the numbers.

Around 2.5 million new people will have been infected and 2.1 million will have died of AIDS in 2007.

Unaids said the decline in AIDS cases, which has been seen in the last two years, was in part due to the life prolonging effects of antiretroviral drugs therapy and to the success of HIV programmes.

Unaids Executive Director Peter Piot said in Geneva: "These improved data present us with a clearer picture of the AIDS epidemic, one that reveals both challenges and opportunities.

"Unquestionably, we are beginning to see a return on investment, new HIV infections and mortality are declining and the prevalence of HIV levelling," Piot said. "But with more than 6,800 new infections and over 5,700 deaths each day due to AIDS we must expand our efforts in order to significantly reduce the impact of AIDS worldwide."