Former South African President Thabo Mbeki said today he was confident an emergency regional summit would salvage a power-sharing agreement between Zimbabwean President Robert Mugabe and the MDC opposition.
Mr Mugabe and opposition leader Morgan Tsvangirai declined to speak to reporters as they arrived for the talks, but Mr Mbeki said he was "very optimistic" they would break a deadlock over control of key ministries in a unity government.
The Southern African Development Community (SADC) convened the meeting amid fears A power-sharing agreement was about to unravel after weeks of fruitless negotiations between ZANU-PF and two Movement for Democratic Change factions.
The accord is seen as key to any effort to pull Zimbabwe out of a deep economic crisis. Inflation is out of control and food and fuel shortages are widespread in the once prosperous nation.
The parties are expected to hold talks late into tonight.
Political analysts say the outcome hinges on how much pressure the 15-nation SADC can put on Mr Mugabe and Mr Tsvangirai to compromise.
Mr Tsvangirai defeated Mr Mugabe in a presidential election on March 29 but by too few votes to avoid a run-off in June. Mr Mugabe won the second round after Mr Tsvangirai pulled out, saying his supporters had been subjected to violence and intimidation.
The rivals and Arthur Mutambara, the leader of a small MDC faction, signed an agreement to form a unity government last month after mediation by Mbeki. The parties then locked horns over control of ministries.