Following the collapse of talks in London it has been left to South Africa to take the diplomatic initiative to encourage Zimbabwe's president, Robert Mugabe, to end political violence which could spark instability, economic collapse and a flood of refugees across the region.

On Thursday South Africa's former president, Nelson Mandela, said that everything was being done behind the scenes to "cool things down". Like the British foreign secretary, Robin Cook, South Africa's president, Thabo Mbeki, has linked a return to law and order and the holding of free and fair elections to the procurement of more money for land reform.

But South Africa has taken a far less combative approach than Britain to try to end the violence which erupted after squatters began occupying white-owned farms, trying to influence events behind the scenes while expressing qualified support for Mr Mugabe.

After last week's meeting of southern African leaders at Victoria Falls, Mr Mbeki called Mr Mugabe a "champion of the rule of law". But privately he called on Mr Mugabe to stop the occupations, hold elections and tone down his rhetoric in return for a commitment to lobby the west for more money for land reform, and the promise of hundreds of millions of rand in loan financing.

The next day some white farmers returned to their homes. But shortly afterwards Mr Mugabe undermined the leaders' agreement when he switched the target of intimidation to black farm labourers and supporters of the opposition, the Movement for Democratic Change, five of whom were killed this week.

Mr Mbeki, whose reluctance to condemn outright Mr Mugabe has earned him criticism from some quarters at home, cancelled a state visit to Zimbabwe because he did not feel it was appropriate to arrive in the run-up to elections.

But he has generally adopted a softer stance, partly because he sympathises with the complexity of the land issue and partly because he fears isolating Mr Mugabe at this stage could trigger a region-wide crisis.

Unrest in Zimbabwe has already been held responsible for the steep decline in the value of the rand, while the South African electricity provider, Eskom, is owed about £80m because Zimbabwe has failed to pay its bill.

"Our biggest concern is that overseas investors will see this domino effect... and ask 'Is South Africa next?' " said the head of the South African chamber of businesses, Kevin Wakeford. "Whether we like it or not, Zimbabwe will have an impact on foreign perceptions. Unfortunately we can't dissociate ourselves from our neighbours."

Moreover, Zimbabwe's land reform crisis draws attention to the South African government's failure to redistribute land at home. Only 6% of land claims have been settled and less than 1% of the land has been redistributed.

Mr Mandela has insisted that there is no prospect of the Zimbabwe crisis being repeated in South Africa, but one recent opinion poll showed 54% of South Africans supporting the squatters in Zimbabwe - almost double the support in Zimbabwe itself.

South Africa is also concerned that a combination of economic collapse and political violence could push a wave of refugees, as well as economic migrants, over the border.

Zimbabwe's opposition leader, Morgan Tsvangirai, yesterday expressed his support for Mr Mbeki's approach, saying: "The South African president has made a significant contribution to trying to resolve the situation here and we are confident that he will continue to do so. We have always favoured an African solution."

Mr Mbeki does have some leverage to encourage Mr Mugabe to comply. He could, for example, threaten to pull the plug on Zimbabwe's electricity supply unless the president makes good on the agreement made at Victoria Falls. But this is unlikely as it could trigger the very economic collapse he is attempting to avert.

That leaves diplomatic pressure, which insiders say will continue through the weekend, to persuade Mr Mugabe that continuing on his present course will end not only in pariah status for himself but will also bring hardship to the entire region.

Useful links:
Zimbabwe Government
Foreign and Commonwealth Office
Movement for Democratic Change