Those talks will be followed by meetings of Zimbabwean negotiators on issues holding back the agreement on forming a unity government, South Africa’s presidency said in a statement.
South African President Kgalema Motlanthe will lead a delegation of regional grouping SADC, Mozambique President Armando Guebuza and mediator Thabo Mbeki, said the statement.
Motlanthe is SADC’s current chairman and South Africa is seen as the country with the most economic and political clout in the region.
While SADC members Zambia and Botswana have criticised Zimbabwean President Robert Mugabe, who has resisted calls to step down, other regional states have failed to persuade the parties to agree despite repeated calls for help from opposition leader Morgan Tsvangirai.
Earlier on Thursday, Tsvangirai demanded the unconditional release of detained party activists before the power-sharing deal with Mugabe could be implemented.
He told a news conference in neighbouring South Africa that he was committed to the agreement, signed by Zimbabwe’s rival political parties in September, but said he lacked a credible partner.
He said there had been breaches of the agreement by Mugabe’s government, including the abduction and detention of opposition activists.
"These must stop immediately and those abducted and illegally detained must be released unconditionally if this agreement is to be consummated," Tsvangirai said.
The power-sharing agreement, held up by a long dispute over key cabinet posts, is still seen as the best chance of preventing total economic collapse in once prosperous Zimbabwe. It now suffers hyper-inflation and food shortages while a cholera epidemic has killed more than 2,000 people.
"I still believe that a political agreement offers the best means of preventing Zimbabwe from becoming a failed state," Tsvangirai said. He said he would return to Zimbabwe on Saturday for the first time since November last year.
U.S.-based Human Rights Watch said at least 43 opposition MDC members had been unlawfully detained since October.
"Zimbabwe authorities are putting lives at risk by secretly detaining MDC members and rights activists. Those unlawfully held should be freed immediately," said Georgette Gagnon, Africa director at Human Rights Watch.
Among those arrested is human rights campaigner Jestina Mukoko, accused with the others of plotting to topple Mugabe, in power since independence from Britain in 1980.
Zimbabwe’s chief justice has ordered urgent medical care for Mukoko and other activists who say they were tortured in police custody. Zimbabwe’s government denies torturing activists.
Mukoko on Thursday appealed to a magistrates court in Harare to allow her to challenge her arrest and detention in the country’s Constitutional Court.
"I think people … should not be handled in the manner I was handled. The experience was frightening, I will not wish it on anyone at all," said Mukoko, wearing a green prison uniform and white sneakers. She broke down once during her testimony.
The deepening humanitarian crises has piled pressure on Zimbabwe’s rival parties to agree and get on with the daunting task of rescuing the country.
More than half Zimbabwe’s population is surviving on food handouts and a lack of funds, combined with projections of more food shortages this year, could make the crisis worse, the aid agency Oxfam said on Thursday. Some Zimbabweans were going for days without meals, Oxfam said.
"Peoples’ lives are in danger because of the lack of food. They are severely weakened and therefore less able to deal with cholera, which has spread across the country, or fight HIV/AIDS," Oxfam’s Zimbabwe director Peter Mutoredzanwa said.