The Health Department wants to use antiretrovirals to treat patients with a CD4 count of 500 or more next year, as recommended by the World Health Organisation's new guidelines.
Currently pregnant women and patients with a CD4 count (a measure of immunity) of 350 or less qualify for treatment.
Health Minister Aaron Motsoaledi told The Times: "The guidelines we are currently following are from WHO, so I see no reason why we should not adopt the new guidelines. If they come with new guidelines, ours is to follow."
But activists and doctors say the department needs to sort out its drugs stocks first.
On Sunday, the UN organisation announced the new guidelines. It said because treatment makes HIV-positive people less infectious, giving it to more people would save millions of lives by 2020.
South Africa has 2million people on ARVs, a regime that resulted in life expectancy jumping by six years last year.
Professor Francois Venter, of the HIV Clinicians' Society, said doctors debated giving ARVs to healthier people extensively last year.
He said that giving ARVs to a million more people would create jobs and keep people in the health system.
"Patients hate being told to come back later [to get treatment]."
But, he said, "It would have been good to sort out supply issues first."
However, with more people on treatment for longer, there is a greater chance of people developing resistance to the drugs, as happened with TB medications.
This can result in premature deaths.
Venter said the research on starting treatment earlier has not factored in "drug interruptions that we are seeing throughout our region".
Mluleki Zazini, general secretary of the National Association for People Living with HIV and Aids, said his organisation had raised concerns about ARV stocks.
Zazini said Motsoaledi had promised to implement a centralised hi-tech stock-monitoring system for drugs.