The government has been widely condemned for refusing to allow the Tibetan spiritual leader, the Dalai Lama, to attend a 2010 World Cup peace conference in Johannesburg on Friday.
Nobel peace laureate and former president FW de Klerk and Archbishop Emeritus Desmond Tutu have both said they will boycott the event in solidarity with the Dalai Lama.
De Klerk was "honour-bound" to respect the invitation that he, former president Nelson Mandela and Tutu sent to the Tibetan spiritual leader last November, at the request of the organisers of the peace conference, the FW de Klerk Foundation said.
Tutu, who was in California, reportedly said yesterday that he had written to President Kgalema Motlanthe asking for an explanation.
"If His Holiness's visa is refused, then I won't take part in the coming 2010 World Cup-related peace conference," Tutu said.
"I will condemn the government's behaviour as disgraceful, in line with our country's abysmal record at the UN Security Council, a total betrayal of our struggle history.
"We are shamelessly succumbing to Chinese pressure. I feel deeply distressed and ashamed."
The Nelson Mandela Foundation said former president Nelson Mandela "would not" attend the event on Friday. Mandela had never planned to attend, the foundation said.
Achmat Dangor, the chief executive of the peace foundation, said Mandela, along with De Klerk and Tutu, was asked to sign invitations to a number of people to attend the Peace Conference organised by the South African Peace Committee.
Motlanthe's spokesperson Thabo Masebe said: "Yes, the president received his [Tutu's] letter. The position we took is that inviting the Dalai Lama at this stage would not be in the interests of South Africa."
He said the reason for South Africa refusing the visa was that it did not want "to remove the world's attention" from the 2010 Soccer World Cup preparations.
"The whole world will be focused on the country as hosts of the 2010 World Cup. We want the focus to remain on South Africa. "A visit now by the Dalai Lama would move the focus from South Africa onto issues in Tibet."
Masebe said China, a major trading partner of South Africa, had played "no role" in the government's decision.
A spokesperson for the Dalai Lama said he was "very disappointed" by the decision.
lThe peace event is expected to discuss ways of using football to fight racism and xenophobia ahead of the 2010 Soccer World Cup. - Sapa