The south African leader was scheduled to give a speech on Aids later on Tuesday.
Zuma's administration has set a target of providing 80 per cent of Aids patients with drugs by 2011.
But reports of shortages of Aids treatment drugs, known as ARVs, at some South African clinics have raised questions about whether the government has the money and the capacity for a massive rollout.
Zuma's policies mark a shift from those of Thabo Mbeki, his predecessor, and Mbeki's health minister, who promoted beets and garlic treatments rather than distributing Aids drugs.
In some ways, Zuma is an unlikely champion for Aids activists.
In 2006, while being tried on charges of raping an HIV-positive woman, he was ridiculed for testifying that he took a shower after sex to lower the risk of Aids.
He was acquitted of rape.
An estimated 5.7 million of South Africa's 50-million population are infected with HIV. Nearly 1,000 South Africans die every day of Aids-related diseases.
A study from the US university of Harvard has concluded that more than 300,000 premature deaths in South Africa could have been prevented had officials here acted sooner to provide drug treatments to Aids patients and to prevent pregnant women with HIV from passing the virus to their children.
About 33 million people worldwide are living with HIV/Aids and there are 2.7 million new cases each year.