South African President Thabo Mbeki has arrived in Harare for talks with his Zimbabwean counterpart, Robert Mugabe, and the opposition's Morgan Tsvangirai.
Mr Mbeki has been mediating between the two sides which have been holding talks in South Africa for more than a week.
Despite a news blackout imposed on the discussions, reports suggest a power-sharing deal may be close.
Zimbabwean government spokesman George Charamba said a "milestone" had been reached but did not elaborate.
He told state media that Mr Mbeki was "going to meet the principals, basically to update them on the progress so far and to consult on how to take the dialogue forward....South African mediators say that talks are aimed at creating some form of coalition but there is disagreement over who would lead a unity government and over Mr Mugabe's exact role.
Mr Mbeki is expected to return to South Africa on Sunday afternoon.