The call came as hundreds of people marched in Mexico City on Sunday to demand better worldwide access to anti-retroviral drugs.
Protesters said the high cost of the life-saving drugs used to treat HIV patients made them prohibitively expensive for many patients.
"In Sub-Saharan Africa there's still limited access to life-saving ARVs, so this march today is an important march to tell the whole world that we need to get ARVs to everybody," Ndulue Nwokedi, a Nigerian doctor, said.
While there have been major advancements in the treatment of Aids since it was first identified in 1981, the anti-retroviral drugs used to slow the spread of HIV in patients are not accessible to all.
It is estimated nearly 10 million people in low- and middle-income countries are in immediate need of treatment for Aids, but only 31 per cent of them are actually receiving it.
Children in danger
The problem is more pronounced for children.
More than 60 per cent of the adults with HIV receive anti-retroviral drugs in Latin America but only about one-third of children do.
|HIV across the world
More than 33 million people infected worldwide
Most cases in Africa: 22.5 million people, 60% women
Asia next biggest group: 4.9 million people. Fastest growing epidemics in Indonesia, Pakistan and Vietnam
Latin America and the Caribbean: 1.9 million people with Brazil home to more than 40%
Experts say less research and funding has been dedicated to medicine for HIV-positive children, who require smaller doses and additional medication to offset the aggressiveness of anti-retrovirals.
And young people are increasingly becoming infected with HIV/Aids.
Worldwide, people aged 15-24 accounted for 45 per cent of people infected with HIV in 2007, according to the 2008 UN Aids report.
In Latin America, 55,000 of the nearly 2 million people with the virus were under 15 years old, the vast majority of them infected by their mothers.
Highlighting the problem for children on Sunday will be Keren Dunaway, a 12-year-old activist who shared the stage on Sunday at the 17th International Aids Conference with the UN secretary-general and the Mexican president.
Keren, among the 25,000 delegates expected to attend the conference, was five when her parents used drawings to explain to her that they and she all had HIV, is one of the most prominent Aids activists in Latin America and editor of a children's magazine on the virus.