South Africa's Thabo Mbeki has held talks in Harare with Zimbabwe's President Robert Mugabe and members of a breakaway opposition faction.
Mr Mbeki has been the chief regional negotiator on the Zimbabwe crisis, and has been trying to persuade Mr Mugabe to form a government of national unity.
However, Morgan Tsvangirai, leader of the main opposition party, declined to meet Mr Mbeki.
Earlier, video emerged of vote-rigging in last month's presidential run-off.
In secretly filmed footage, a prison guard and fellow prison officers were shown being forced to vote for President Robert Mugabe in front of superior officers.
The guard, Shepherd Yuda, filmed the vote-rigging for Guardian Films. He has now fled Zimbabwe.
Meanwhile, a White House spokesman said leaders of the Group of Eight (G8) developed nations were likely to "strongly condemn" Mr Mugabe over the poll when they meet in Japan on Monday, the AFP news agency reports.
Mr Mbeki is now heading to Japan following his crisis talks.
He told reporters after the talks that everyone involved should move swiftly towards finding a solution.
"It is the view of the facilitators and the Zimbabwean leadership that we need to move with speed," he said.
The main opposition party, the Movement for Democratic Change (MDC), pulled out of the run-off vote citing campaign violence.
Mr Mugabe has said the opposition must accept him as leader before any talks can take place on ending the country's political crisis.
Mr Mugabe met Mr Mutambara, head of a breakaway opposition faction
A spokesman for Mr Tsvangirai said he had refused to attend a meeting at State House in Harare because doing so would imply recognition of Mr Mugabe as president following his controversial re-election.
The BBC's Peter Greste in Johannesburg says the MDC is not comfortable with the way Mr Mbeki is managing the mediation process, so it sees little point in taking part in talks with him.
There is not a great deal of confidence that Zimbabwe's political stalemate will be resolved any time soon, our correspondent adds.
Mr Mbeki told reporters he hoped to meet Mr Tsvangirai at a later stage, AFP reports.
"We agreed that MDC-Tsvangirai has to be part of the negotiations so we are hoping that the process will take place with them," Mr Mbeki is quoted as saying.
He said he had agreed to come to Harare partly as a result of a request from Mr Tsvangirai but that the latter had subsequently asked for the meeting to be postponed.
Mr Tsvangirai had indicated that he wanted to wait for the input of the African Union in the mediation process, Mr Mbeki added.
The MDC leader has previously called for Mr Mbeki to be replaced as the regional mediator, accusing him of favouring Mr Mugabe.
Mr Mbeki held brief talks with Mr Mugabe before the pair were joined by members of a breakaway faction of the MDC.
They included the faction's leader, Arthur Mutambara, its secretary-general, Welshman Ncube, and the latter's deputy, Priscilla Misihairibwi-Mushonga.
Mr Mutambara's faction split from the MDC in 2005. It pledged to work with the MDC in April ahead of the run-off vote, having supported another candidate in the first round of voting in March.
Last week, Mr Tsvangirai said the violence had to end before talks on sharing power could be entertained.
The MDC says 5,000 of its members are still missing and that more than 100 of its supporters have been murdered in continuing post-poll intimidation.
A small group of African states has joined the European Union, the US and other Western nations in criticising the way the election was run.
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