Former South African president Thabo Mbeki said he was hopeful that power-sharing talks in Zimbabwe would produce a breakthrough as he arrived Monday in Harare for a regional summit.

“Progress on the talks is very good,” Mbeki told reporters, adding that he was “very optimistic” about finalising plans for a unity government in the talks Monday.

Mbeki brokered the unity agreement signed six weeks ago, calling for Zimbabwe’s long-time leader Robert Mugabe to remain as president while opposition leader Morgan Tsvangirai becomes prime minister.

But the deal threatens to collapse over bitter disagreements about how to divide control of the most powerful ministries – particularly home affairs, which oversees the police.

Key regional leaders are meeting in Harare to try to salvage the deal, seen as the best hope for ending Zimbabwe’s political turmoil and pulling the country from economic ruin.

South Africa’s new President Kgalema Motlanthe arrived earlier Monday for the talks, which will also gather Swaziland’s Prime Minister Barnabas Dlamini and Angolan foreign minister Assuncao dos Anjos.

Mozambican President Armando Emilio Guebuza was also expected to attend the meeting.