However, the agreement and signing off of the details of constitutional amendment No 19 on Thursday does not mean that a unity government is now an inevitable reality.
Other issues that opposition leader Morgan Tsvangirai had originally put on the agenda were not resolved because negotiators from Zanu-PF and the faction of the Movement for Democratic Change led by Arthur Mutambara declined to discuss them, saying they did not have instructions to do so from their principals.
The control of the Ministry of Home Affairs was not dealt with because negotiators from Zanu-PF and the MDC-M said it had already been dealt with by the South African Development Community.
"Issues that the SADC has dealt with already, like the Ministry of Home Affairs, should be left to be resolved by the regional body," said one of the negotiators.
The SADC resolved at a recent summit that Tsvangirai and President Robert Mugabe should share Home Affairs, a solution that Tsvangirai has vehemently rejected.
"The SADC has to continue dealing with issues like Tsvangirai’s unrelenting demands on sharing ministries equitably," the source added.
Tsvangirai issued a scathing statement on Tuesday, saying he would no longer take part in the negotiations officially until Thabo Mbeki was removed as mediator.
Tsvangirai said his team would remain in the discussion on a "without prejudice basis" until Mbeki’s removal. He said he had already written to President Kgalema Motlanthe, in his capacity as chairperson of the SADC, demanding Mbeki’s removal.
However, his representative in the negotiations signed up all the agreed details of constitutional amendment No 19.
Mugabe is now expected to proceed with gazetting the constitutional amendment, after which it will be put to parliament for approval to give legal force to the unity agreement signed amid much pomp and fanfare on September 15.
It is not clear what Tsvangirai’s attitude to the agreement on constitutional amendment No 19 is going to be in light of his declaration that his negotiators were participating in the deliberations unofficially.
Even if Tsvangirai accepts the agreed details of the constitutional amendment, and it is subsequently gazetted and approved by parliament, he is unlikely to join a unity government until he is given full control of Home Affairs and his other demands on the equitable distribution of governors and the composition of the proposed national security council are addressed.
Although both Zanu-PF and the MDC-T had brought two different versions of what they wanted in constitutional amendment No 19, the sources said consensus had not been difficult to reach. This was because negotiators had agreed to exclude details that were not part of the September 15 deal.
A source in Mutambara’s faction dismissed as mere "grand-standing" a declaration by Tsvangirai that he wants Mbeki removed.
"There is no way the SADC leaders are going to convene a summit to remove Mbeki," he said.