Tsvangirai, who boycotted a widely criticised June 27 election run-off, said Mugabe must first stop attacks on opposition supporters and demanded that negotiations take place on the basis of a March 29 first round vote, which he won.

"Significantly the conditions prevailing in Zimbabwe are not conducive to negotiations. If dialogue is to be initiated, it is essential that ZANU-PF stops the violence, halts the persecution of MDC leaders and supporters," he told a news conference in Harare.

Tsvangirai said his Movement for Democratic Change (MDC), which defeated Mugabe's ZANU-PF in parliamentary election, should be recognised as Zimbabwe's legitimate government.

Mugabe's officials earlier welcomed the call from African Union (AU) leaders at a summit on Tuesday to join talks with the opposition on a joint administration to end the crisis in Zimbabwe, whose economy is ruined.

"The AU resolution is in conformity to what President Mugabe said at his inauguration, when he said we are prepared to talk in order to resolve our problems," Information Minister Sikhanyiso Ndlovu told Reuters.

"We are committed to talk, not just with Tsvangirai but to other parties as well."

Tsvangirai said talks would be meaningless unless the African Union sent a permanent envoy to expand mediation efforts by South African President Thabo Mbeki, criticised for being too soft in his diplomacy with Mugabe.

Despite the AU support for a power-sharing deal modelled on the one that ended post-election violence in Kenya earlier this year, disagreement over who should lead the government could prove an insurmountable obstacle.

Mugabe, 84, was sworn in for a new five-year term on Sunday after election authorities announced he had won about 85 percent of the vote in a run-off, which was condemned by monitors and much of world opinion as violent and unfair.

Mugabe has branded the MDC a puppet of former colonial power Britain and the United States and vowed to never let it rule Zimbabwe. Western countries are discussing whether to toughen sanctions on Zimbabwe's leaders.

French Foreign Minister Bernard Kouchner, whose country has take over the European Union presidency, said on Tuesday the EU would only accept a government led by Tsvangirai. The European Commission repeated that line on Wednesday.

"Any transitional government must include Morgan Tsvangirai as prime minister or head of government," Commission development spokesman John Clancy told a briefing in Brussels.

Zimbabwe's once prosperous economy is racked by the world's highest rate of hyper-inflation, food and fuel shortages and 80 percent unemployment.