"It now has more people with HIV infections than any [other] country - 5.6 million. That is due to a lack of political commitment before," said Sheila Tlou, UNAids regional director for East and Southern Africa.

"However, there is a turnaround in President Jacob Zuma's government, which is committed in its fight against HIV and Aids," she said.

"By 2020 there will be massive reductions in South Africa."

Zuma, who has dramatically expanded the country's Aids treatment programme since taking office in 2009, last month unveiled a plan to halve the number of HIV infections over the next five years.

The five-year plan is the first that has been drafted since the 2008 ousting of President Thabo Mbeki and his health minister, Manto Tshabalala-Msimang.

Tlou said east and southern Africa were known as "the centre of the epidemic" because, of the world's 34million people living with HIV, almost three-quarters lived there.

"One of our targets is to reduce new infections by 50% by 2015," she said.

But Tlou noted that fading commitment by the Global Fund to Fight Aids to combating tuberculosis and malaria could have a negative effect on the fight against the disease.

"There has been quite a lot of progress since 1997, with a 25% reduction in new infections in our region," she said.

Steve Kraus, UNAids director for Asia and the Pacific, said important progress had been made in big countries such as China, India and Indonesia, and in smaller countries such as Fiji and Samoa.

Kraus said China had adopted a policy of zero tolerance of HIV.

This was later adopted by the 10 ASEAN nations.

"China is increasingly funding its national response [to HIV] and added $1-billion last year," he said.