Zimbabwe's political impasse is becoming a major hindrance to regional stability and a summit this weekend must break the deadlock, the South African government said on Thursday.

Zimbabwe's President Robert Mugabe and opposition leader Morgan Tsvangirai signed a power-sharing deal on 15 September, agreeing to form a unity government to end months of political turmoil.

But the deal is stalled over disputes about how to divide control of the most powerful cabinet posts, particularly the home affairs ministry, which oversees the police.

"We believe South Africa and the region cannot be held to ransom by parties who are failing to reach agreement on the allocation of cabinet posts," government spokesperson Themba Maseko told reporters in Pretoria.

"This is becoming a matter of extreme concern for us and we will be taking quite a hard stance to make sure that agreement is reached," he said.

"The failure of the parties to agree is something that is becoming a major political hindrance to the stability that we desire" in southern Africa, Maseko said.

South Africa will host an emergency summit of the 15-nation Southern African Development Community (Sadc) on Sunday in a bid to salvage the unity accord.

"It's government's view that the heads of state must now take urgent steps to make sure political solutions are found," Maseko added.

He would not say what steps regional leaders were being urged to take, but said South Africa would be "making proposals on how we think the situation should be expedited".

"We believe the heads of state have played a key role in making sure that the Zimbabwean problem is seen as an African problem with African solutions being required," Maseko said.

"Now, the heads of state are being tested to see if they can actually deliver a political solution to Zimbabwe's problems," he added.

Tsvangirai won a first round presidential election in March but pulled out of a June run-off, accusing the Mugabe's regime of orchestrating a campaign of political violence that left more than 100 of his supporters dead.

Sadc has held numerous meetings aimed at pressing the rivals into a deal, and tasked former South African president Thabo Mbeki with mediating in the crisis.

He brokered the power-sharing deal, and resumed his mediation last month in a bid to resolve their dispute over forming a cabinet.

So far, Sadc has failed to take a strong, unified stand on Zimbabwe, despite the country's stunning economic collapse that has sent waves of migrants across its borders in search of work.

AFP