Both veteran President Robert Mugabe and Prime Minister Morgan Tsvangirai greeted Zuma at the airport, where he received a 21-gun salute and his signature song, the anti-apartheid anthem "Umshini Wami" (Bring Me My Machine Gun), was played.

After greeting officials on the tarmac, the three leaders left for an official dinner at Mugabe’s residence. Zuma was due to hold talks with the leaders later in the evening.

Mr Zuma is hoping to break the deadlock that is paralysing Zimbabwe’s coalition government established six months ago. The two majority partners in the coalition administration – Prime Minister Morgan Tsvangirai’s Movement for Democratic Change and Mr Mugabe’s ZANU-PF, which has ruled since independence in 1980 – are at loggerheads over a range of issues, including a fresh wave of farm invasions by Mr Mugabe’s supporters.

An opinion poll carried out in May, released this week, suggests that support for Zanu-PF has collapsed to less than 10 percent of the electorate, while Mr Tsvangirai’s MDC would win a comfortable majority in any fresh elections with 57 percent of the votes.

Gwede Mantashe, the secretary general of South Africa’s ruling African National Congress and one of Mr Zuma’s closer allies, cited today the continued harassment and arrest of parliamentarians from the MDC as an example of “deviant” behaviour which he suggested Mr Zuma would be vocal in condemning.

“In our view all these issues are a hindrance to progress and that’s why we will always be vocal. A neighbour, whether you like it or not, is a friend because you do not have a choice.”

The six-month-old unity government, created as a compromise to the deadlock resulting from last year’s parliamentary elections, had given all sides in Zimbabwean politics a chance to “sober up” and they had to make the best of it, said Mr Mantashe.

During his two-day visit, Mr Zuma will meet Mr Mugabe as well as the MDC leader Morgan Tsvangirai, who is prime minister, in his capacity as chairman of the regional grouping the Southern African Development Community, his office said this week.

Under Mr Mbeki’s administration, which came to an end last September when the ruling African National Congress turned against him, South Africa drew criticism for its reluctance to criticise Mr Mugabe in public.

The meeting is particularly crucial for Mr Tsvangirai, who is more likely to get sympathy and possibly even support from Mr Zuma than from the next head of SADC, President Joseph Kabila of the Democratic Republic of Congo, a staunch Mugabe ally, who takes over next month. By the same token Mr Mugabe has every reason to stall tomorrow’s discussions confident that when Mr Kabila, who owes his position to the military support sent to the DRC by Mr Mugabe a decade ago, takes over he will have even greater regional support than he has at present.

Mr Mantashe conceded that South Africa’s policy under Mr Zuma did not differ fundamentally from Mr Mbeki’s but stressed that the new administration would speak out more.

“The only difference will be that President Zuma will be more vocal in terms of what we see as deviant behaviour by our neighbours. That’s why President Zuma is heading to Zimbabwe, to engage them,” he said.

There is mounting concern that ZImbabwe’s crisis could worsen in the months ahead. Even when ministers make decisions they are finding it difficult to implement them while a rash of actual and threatened strikes over pay – state doctors, miners, civil servants, schoolteachers – reflects mounting impatience at the interim government’s failure to deliver on some of the extravagant promises made six months ago.