A South African peace conference involving Nobel laureates was postponed yesterday over Pretoria's refusal to grant a visa to the Dalai Lama, angering the grandson of Nelson Mandela.

Mandla Mandela, who helped plan the event, said the rejection of the Dalai Lama was "unfortunate" and tainted his illustrious grandfather's efforts to bring democracy to South Africa.

"It's a sad day for South Africa. It's a sad day for Africa," he told reporters.

Nelson Mandela, along with Archbishop Desmond Tutu and former President FW de Klerk, were to host the peace conference on Friday in Johannesburg, bringing together Nobel laureates from around the world.

The conference was to discuss how soccer can fight racism and xenophobia, as South Africa prepares to host the 2010 World Cup.

Officially South Africa says it does not want a visit by the Dalai Lama to draw attention away from preparations for the World Cup, insisting that his visit has merely been "postponed".

Thabo Masebe, spokesman for President Kgalema Motlanthe, said he could not say when the Dalai Lama would be allowed to visit.

"We made the decision. We stand by the decision. Nothing is going to change," he told reporters.

Now that the peace conference has been scuppered, the event's chairman Irvin Khoza said he did not know when it would be rescheduled.

Archbishop Tutu and Mr De Klerk had earlier indicated they would withdraw from the event over the controversy, while the Nobel peace committee said it would have to withdraw its support unless the Dalai Lama was allowed to attend.

"For me personally, and the role my grandfather has played in founding our democracy, together with his colleagues, this rejection by the government to not issue a visa to the Dalai Lama is really tainting our efforts of democracy," Mandla Mandela told a news conference.

"I don't think that as sovereign independent country, we need to succumb to international pressures," he said.

South Africa's government has denied that the Dalai Lama's visa was rejected due to pressure from China, a key trading partner. But Chinese diplomats told local media that Beijing had urged South Africa to deny the visit or risk damaging bilateral relations.