"I know that he is no longer attending," said ANC spokesman Tiyani Rikhotso. Zuma had other engagements after returning from travel abroad, he said.

A South African women's rights group had protested about the American boxer's appearance at a gala banquet at Johannesburg's Emperors Palace casino to raise funds for a charity. Zuma was expected to be the keynote speaker.

Tyson served three years in an Indiana prison following a 1992 rape conviction.

South Africa has one of the world's worst crime records, including for rape, and Tyson's presence angered the rights group, the One in Nine, whose name refers to the rate of reported rape cases in South Africa.

"Tyson has a poor track record and well-articulated disrespect for human rights in general and women's rights in particular. Some of his well-known acts of violence in both the public and private domain have included: rape of (an) 18-year-old woman in 1992," the group said in a statement.

"He has proved less than ideal as a role model in either his sporting or personal life."

Zuma was acquitted of rape charges in 2006. He is due to go on trial in August for racketeering, money-laundering and other charges tied to an arms deal.

He is likely to become South Africa's president in 2009 if he defeats the charges in court.