Mbeki has been mediating efforts in South Africa this week to persuade Mugabe to share power with Tsvangirai's Movement for Democratic Change party, which has accused Mugabe's regime of killing scores of its supporters in the run-up to presidential elections this year. Tsvangirai pulled out of a run-off election as a result of the escalating violence.

With Mbeki's decision to go to Zimbabwe, some observers say a power-sharing deal may be near, the BBC reported Saturday. The South African president was expected to return home Sunday, sources told the broadcaster.

Despite an official news blackout on the talks, South African media outlets are saying an emerging deal could see Mugabe keeping a grip on the presidency with Tsvangirai becoming prime minister with executive powers. The BBC said Mbeki is facing pressure to produce a workable deal ahead of this month's summit of the South African Development Community.