South Africa believes Zimbabwe is on track to form a unity government but is extremely concerned about the food and cholera crises of its northern neighbour, government spokesman Themba Maseko said on Thursday.

Pretoria has welcomed a draft deal to amend the Zimbabwean constitution to create the post of prime minister for opposition leader Morgan Tsvangirai and will press the country's political rivals to sign it, he told a media briefing following Cabinet's fortnightly meeting on Wednesday.

"We will put pressure on the political principals to sign as soon as possible," he added.

In the meanwhile Cabinet has called an urgent ministerial meeting to discuss ways South Africa could help stop a mounting death toll from starvation and disease in Zimbabwe, he said.

"President [Kgalema] Motlanthe will convene a meeting of key ministers to consider ways in which South Africa could work with other countries in the region, donor organisations and NGOs to address the urgent need for food and other humanitarian needs.
"We believe people are dying of starvation and we cannot fold our arms," he said.

Maseko said South Africa planned to make "all the necessary interventions" to help fight the cholera epidemic in Zimbabwe, which has claimed 565 lives and seen a national emergency declared.

According to the latest reports more than 12,000 people in Zimbabwe are infected with the virulent, water-born disease.

Maseko said government's efforts to combat the cholera outbreak had so far focused on treating afflicted Zimbabweans who have come into South Africa, but these had to be extended across the border to prevent an influx of carriers.

The government was therefore talking to NGOs and other countries in the region about how they could best respond.

"It is very clear that if we keep on providing services inside the country without any intervention inside Zimbabwe, we will create a magnet for people to come across the border and receive medical attention."

Maseko added that cabinet has decided to keep on hold a R300-million aid package to Zimbabwe, which was aimed at alleviating the country's agricultural crisis.

"Even if that money was released tomorrow it still would not be able to put food on the table immediately," he said.

Nearly half of Zimbabwe's population is expected to need food aid by January.

Motlanthe has warned that Zimbabwe would "collapse" under the weight of its humanitarian crisis unless it found a way out of political deadlock.

A power-sharing deal Tsvangirai and arch-rival Robert Mugabe signed in September has stalled over disputes about the powers of the new premier and the division of cabinet posts.

The tentative deal on a constitutional amendment was made at talks in South Africa in late November as mediator Thabo Mbeki tried to salvage the political accord.