South Africa plans to spend $2.2 billion over two years to buy HIV/AIDS drugs for public hospitals, a government minister said on Monday, as a study shows the prevalence of the virus is rising.

Speaking at a manufacturing plant of drugmaker Aspen Pharmacare, Trade and Industry Minister Rob Davies said the government aims to buy three quarters of the drugs from local manufacturers.

"We are on the cusp of a very important tender worth 24 billion rand ($2.2 billion) by the Department of Health that is for the procurement of anti-retrovirals for 2015," Davies told reporters at Aspen's factory in the coastal city of Port Elizabeth.

South Africa awarded a $667 million two-year contract in 2012 to pharmaceutical firms including the country's biggest, Aspen, and U.S.-based Abbott Laboratories.

Aspen, which won more about a third of that contract, would also be bidding this year and its chief executive Stephen Saad said his company was aiming for more than a 50 percent share.

South Africa has one of the world's heaviest HIV/AIDS case loads and its biggest treatment program. But despite government efforts to spread the treatment, medical charities warned last year that many clinics were running out of the life-saving drugs.