South African President Thabo Mbeki met Zimbabwe's Robert Mugabe and his rival on Wednesday to try to mediate an end to a violent election crisis.

Mugabe faces a presidential election run-off next week against opposition leader Morgan Tsvangirai and stands accused by opponents, Western countries and human rights groups of orchestrating a campaign of killings and intimidation.

Mbeki, who has led regional mediation efforts in Zimbabwe, has been criticised for his quiet diplomatic approach that has failed to end a political and economic crisis that has driven millions of people into neighbouring states.

The head of South Africa's ruling party voiced doubts over whether the June 27 vote could be fair, a strong indication that patience was running short with Mugabe in Africa as well as among his traditional Western critics.

The South African president spent 3-1/2 hours with Mugabe at the Zimbabwean ruler's official residence the second biggest city, Bulawayo, but made no comment to reporters afterwards.

Mbeki earlier met Tsvangirai in Harare, the opposition Movement for Democratic Change said. The party confirmed the meeting but offered no further comment.

Mugabe lost the first round vote to Tsvangirai on March 29, but the opposition leader did not get the outright majority needed to avoid a second round, according to official results.

ZUMA DOUBTS

In his bluntest language yet on the crisis, African National Congress leader Jacob Zuma criticised the violence that has engulfed Zimbabwe since the March 29 general election.

"I think we'll be lucky if we have a free election," African National Congress leader Jacob Zuma told Reuters after a speech in the South African capital Pretoria. Zuma has taken a much tougher line on Zimbabwe than Mbeki.

Mugabe blames his foes for the violence and has threatened to arrest opposition leaders over the troubles. Tsvangirai's party says at least 66 people have been killed by supporters of Mugabe's ZANU-PF.

The United States and former colonial power Britain also accuse Mugabe of trying to intimidate opponents to ensure he keeps his 28-year hold on power.

"It is time for the leaders of Africa to say to President Mugabe that the people of Zimbabwe deserve a free and fair election," U.S. Secretary of State Condoleezza Rice told reporters in Washington.

Rice said she and the foreign minister of Burkina Faso would chair a round-table at the United Nations on Thursday to discuss Zimbabwe.

U.N. Secretary-General Ban Ki-Moon said violence, arrest of opposition leaders and intimidation threatened the vote.

"Should these conditions continue to prevail, the legitimacy of the election outcomes would be in question," Ban told an informal session of the General Assembly.

The World Council of Churches called for U.N. action to put an end to "atrocities" committed by the Zimbabwe authorities, saying churches had also been subjected to violence.

Rwandan President Paul Kagame heaped scorn on Mugabe and the ZANU-PF for vowing not to surrender power if beaten. "For me the question that it raises is why do you even call for elections?" Kagame said in a news conference in Rwanda's capital, Kigali.

Nobel laureate Desmond Tutu also expressed his pessimism. "It's just one of those awful, awful things that is happening there, and I can't myself see how we are ever going to be able to have a free and fair run-off," Tutu told Reuters Television.

Although he is still revered in Zimbabwe for his role in liberating the country from colonial rule, Mugabe has lost support due to an economic crisis that has brought hyperinflation and chronic food shortages.

U.N. food agencies said on Wednesday that more than 5 million people in Zimbabwe risk going hungry by early next year as production of the staple maize in 2008 would be almost 30 percent lower than last year.