Mugabe is currently trying to push through constitutional amendments that would allow him to appoint a cabinet alone - further antagonising the MDC.

Cholera epidemic

"The situation has just gone beyond a situation where we could say 'wait and see'"

Jacob Zuma, ANC leader

Officials say the political impasse has crippled the Zimbabwean economy, further worsening what was already a grave humanitarian situation.

Food shortages and hyper-inflation have forced millions  to flee the country. Humanitarian groups say those who remain increasingly face malnutrition and disease.

An outbreak of cholera has already killed around 300 people and infected as many as 6,000 others, prompting fears the epidemic will spread into neighbouring countries as refugees continue to flee Zimbabwe. 

Efforts by mediators like Jimmy Carter, ex-US president, and Kofi Annan, former UN secretary-general, to force through a deal that is acceptable to both sides have so far failed to yield results.

Carter and Annan, clearly exasperated after Mugabe's government blocked their scheduled visit to Harare, denying them visas on the grounds their visit was unnecessary, called on regional leaders to help enforce the implementation of the unity government.

Sanctions threat

Annan, flanked by Carter, and human rights campaigner Graca Machel, the wife of Nelson Mandela, said on Monday: "Sadc [the Southern African Development Community leaders group] must bring its full weight to bear... I think it is clear that Sadc should have done more."

Machel, who, along with Carter and Annan, is part of a group called the Elders, lauded South Africa's move to withold $28 million in food aid from Zimbabwe in an attempt to force the leadership to share power.

"That's a good tone. Maybe other Sadc nations should consider doing the same," she said.

Talks led by Thabo Mbeki, former South African president, are expected to resume on Tuesday in South Africa. 

South Africa's ruling African National Congress (ANC), backed by Mugabe during its decades-long struggle to overthrow apartheid, will also send a delegation to Zimbabwe to assess the situation, said ANC leader Jacob Zuma.

Zuma also voiced his alarm at the rapidly-deteriorating humanitarian situation in Zimbabwe.

"The situation has just gone beyond a situation where we could say 'wait and see'," he said.