"The president and the two leaders of the MDC formations met this morning in consultation over the setting up of government but failed to conclude their consultation," Charamba said.
Arthur Mutambara, leader of a smaller faction of the opposition Movement for Democratic Change (MDC), also attended the meeting.
Mbeki’s spokesman said Mbeki would not be going to Zimbabwe to mediate Saturday’s talks.
"He is not going to Zimbabwe this weekend," spokesman Mukoni Ratshitanga told Reuters.
Officials from both Tsvangirai’s main MDC party and Mutambara’s faction declined to comment on the talks.
Talks between Mugabe’s ruling ZANU-PF and the MDC have reached an impasse over who will control key ministries in a unity government to be established under the Sept. 15 power-sharing deal.
The opposition accuses Mugabe’s party of trying to assign it a junior role in government and says only mediation can break a deadlock in talks on forming a cabinet.
But ZANU-PF said it did not see any immediate need for mediation and Mugabe had expressed confidence the cabinet would be named this week. Tsvangirai and his officials say a deal is not imminent.
A meeting between Mugabe and Tsvangirai on Tuesday failed to lead to a breakthrough, raising fears the deal could break down.
Without a breakthrough, Zimbabwe’s economy could worsen still further. The once-prosperous nation is crumbling under inflation of about 11 million percent — the highest in the world — and chronic food shortages.