Ex-South African Deputy President Jacob Zuma has denied undermining the fight against Aids by having unprotected sex, as his rape trial continues.
Mr Zuma is a veteran of the struggle against apartheid
The former head of the National Aids Council said the risk of contracting the virus was small for a healthy man. Aids activists condemn his statement.
He denies raping a family friend and HIV positive Aids activist, saying they had consensual sex.
More than 5m South Africans have HIV - the highest number in the world.
Mr Zuma - previously seen as a possible future president - retains considerable popularity. His supporters see the charge as a political conspiracy.
The BBC's Peter Biles in Johannesburg says Mr Zuma's evidence has however caused outrage and dismay among local Aids activists.
"Why do you, a man who could still be president of this country, why were you prepared to take that risk?" asked state prosecutor Charin de Beer as she questioned Mr Zuma in the Johannesburg High Court.
He said he regularly used condoms and had often preached the government's policy that people should use condoms to prevent the spread of HIV.
Having unprotected sex is thought to be the main way in which Aids is spread in Africa.
Mr Zuma, 63, insisted that the woman, 31, who may not be named, had initiated the sexual encounter.
"If she had said no, I would have stopped there and gotten up and left," he said.
The prosecution also suggested that he raped the complainant because she would never have consented to sex without a condom.
Vicci Tallis from the Gender Aids Forum said: "Statements like [Mr Zuma's] can throw years of hard work down the drain".
Last week, the defence failed in an application to have the rape charge dropped.
The case has attracted huge publicity and court sessions have drawn demonstrations by groups both for and against Mr Zuma.
Women's groups have been critical of the trial and the cross-examination of the 31-year-old woman at the heart of it, who is HIV positive and an Aids activist.
Jacob Zuma's supporters say the trial is political
Supporters of Mr Zuma have at times stood outside the court and jeered as she arrived at the courthouse.
Mr Zuma - a veteran of the ANC struggle to end apartheid and a favourite of the party's left wing - was once thought a likely successor to Thabo Mbeki as South African president.
But the allegations of rape and corruption are thought by many to have ended that prospect.
A separate corruption trial is scheduled to begin in the Durban High Court in July. Mr Zuma denies the corruption charge.