Zimbabwe's political rivals are expected to resume power-sharing talks on Saturday at a meeting of the Southern African Development Community in Johannesburg.
There is mounting pressure to find a way to end the crisis, with talks being led by South African President Thabo Mbeki.
South African Foreign Minister Nkosazana Dlamini Zuma says "this matter must be resolved."
Three days of discussions this week between President Robert Mugabe, and opposition leaders Morgan Tsvangirai and Arthur Mutambara, ended after Mr Tsvangirai refused a proposed deal.
Mr Mbeki has said he remains confident a quick resolution is still possible.
Millions of people have fled Zimbabwe to escape the world's highest inflation rate of 2.2 million percent, widespread unemployment, and chronic shortages of food and fuel.
Boycott of SADC
Botswana's president will boycott the meeting because Mr Mugabe has been invited.
In what's described as an unprecedented move, Botswana is urging the SADC not to give legitimacy to the second round of Zimbabwe's presidential election.
A statement issued by the goverment says the run-off election on 27 June violated the core principles of SADC, the African Union and the United Nations.
Mr Mugabe was the only candidate in the poll.
Botswana says he should not attend SADC gatherings until a power-sharing deal is reached in Zimbabwe.
The stance is the toughest taken by Zimbabwe's neighbours.