Zimbabwe's opposition leader Morgan Tsvangirai has rejected an African Union decision to keep South African President Thabo Mbeki as the only mediator tasked with resolving his country's political crisis.

Mbeki was reconfirmed as the sole mediator between Zimbabwe's government and disgruntled opposition leaders at this week's AU summit. Tsvangirai said his party will not sit down at the negotiating table without an additional mediator.

"It is our position that unless the mediation team is expanded to include at least one permanent representative from the African Union and the mediation mechanism is changed, no meaningful progress can be made toward resolving the Zimbabwe crisis," he said.

"If this does not happen, then the MDC will not be part of the mediation process."

Tsvangirai had previously called for Mbeki to step down. He had accused Mbeki of in effect appeasing Robert Mugabe because of his uncritical stand regarding the Zimbabwean president in the wake of the country's questionable national elections.

Mugabe was sworn in for his sixth term after winning a run-off vote last week. Tsvangirai, whose supporters had been targeted by violence in recent weeks, had withdrawn from the race. As a result, Mugabe was the only viable candidate in an election that was widely condemned in the West.

Mbeki said after the AU summit that only Zimbabweans can determine their leadership, a response that undercut a European Union call for Tsvangirai to lead a coalition government.

Tsvangirai had also said Wednesday that conditions were not right for negotiations that may lead to a coalition government. He said any talks of a unity government must be based on results of the country's March 29 vote, the first round of national voting, which Tsvangirai won.

Archbishop Tutu "distressed"

Retired South African Archbishop Desmond Tutu said Wednesday he was "deeply disappointed" and "distressed" at the African Union's failure to take a forceful stand against Mugabe and his government.

"I am distressed that (AU leaders) have not thought it was important to declare the illegitimacy of the runoff and the illegitimacy of the Robert Mugabe administration," he told CTV's Canada AM by phone from Cape Town, South Africa.

"They hardly seemed to have referred to the violence and the suffering being undergone by the people of Zimbabwe," Tutu said.

Tutu said Zimbabwe's opposition party should have a senior role in any coalition government that may be negotiated.

He said African leaders paid "scant attention to the violation of human rights" in Zimbabwe. Mugabe was warmly received by AU leaders when he showed up at the summit on Monday.

Many officials at the meeting were reluctant to publicly criticize Mugabe, but instead were said to be maneuvering behind-the-scenes to force him into a power-sharing deal with Tsvangirai. The leaders failed to reach a deal.

Tutu said he was encouraged that some African critics of Mugabe emerged Tuesday. The Associated Press reported Botswana's vice president had released a statement saying Zimbabwe's election results do "not confer legitimacy on the government of President Mugabe."

Canada has implemented travel, work and study sanctions against Zimbabwe. The U.S., Britain and other European countries have all widely condemned the runoff. The U.S. is also pressuring the UN to impose an arms embargo on Zimbabwe.

With files from The Associated Press