Mugabe and Morgan Tsvangirai, leader of the opposition Movement for Democratic Change (MDC), have been deadlocked in talks to form a unity government since a power-sharing agreement in September, with neither side showing any sign of compromise.
Mugabe has urged the opposition to join a unity government but has made it clear he would not hesitate to name one without them. Tsvangirai has said no deal is possible unless party activists are released from jail.
The 15 state Southern Africa Development Community (SADC) summit hosted by South African President Kgalema Motlanthe hopes to break the impasse as Zimbabwe teeters on the brink of economic collapse and grapples with a humanitarian crisis.
Similar summits have failed to push the political process forward largely because SADC is divided over how it should deal with Mugabe, analysts say.
SADC members such as Botswana and Zambia have taken a tough line on Mugabe, who has been in power since independence from Britain in 1980, but others still revere him as a former liberation hero.
Botswana’s President Seretse Khama Ian Khama, one of Mugabe’s harshest critics, will also attend the summit. Ties between Zimbabwe and neighbouring Botswana became strained after Khama said a new election was the only solution to the crisis.
Regional leaders including SADC mediator and former South African President Thabo Mbeki failed last week to persuade the rivals to form a government.
Mugabe has accused the MDC of working with Western powers to oust him. He has remained defiant through several rounds of talks that have stalled over the control of cabinet ministeries.
Western leaders want Mugabe to step down and are also pushing for a democratic government to embrace economic reforms before billions of dollars in aid is offered.
Without a political settlement, it is also unlikely sanctions imposed on Zimbabwe by Western countries will be lifted.
Zimbabwe, ravaged by the world’s highest rate of inflation, severe food and fuel shortages and a virtually worthless economy, also faces Africa’s biggest cholera epidemic in a decade.
The water-borne disease has killed nearly 2,800 people and infected more than 40,000 since it broke out in August.