The talks came after Mugabe and Morgan Tsvangirai, the MDC leader who withdrew from the June 27 poll complaining of widespread violence and intimidation, signed a memorandum of understanding in Zimbabwe's capital Harare on Monday.
Under the terms of the framework agreement signed, both sides are observing an official media blackout. However, it is understood that the talks are taking place in the South African capital Pretoria.
Ratshitanga said that even if negotiators missed a two-week deadline set under that agreement, it did not mean the end of talks.
"It does not mean if the talks are not done in two weeks, that the talks will collapse," he said.
National unity government
The main aim of the Pretoria talks is believed to be to work towards the creation of a government of national unity, but the two sides differ on who should lead it and how long it should stay in power.
However, Business Day, a South African financial daily, reported on Thursday that the two sides are close to reaching a deal.
Citing sources from both parties and people familiar with the talks, the newspaper said that a final settlement can be reached as soon as the parties had already agreed on many issues.
"They have agreed on most of the issues, except mainly the framework for a new government. The deal is basically done, but what remains are a few issues of detail, implementation and logistics," Business Day quoted a source as saying.
While Mbeki is overseeing the talks, he was not present on Thursday as he is heading to France for a one-day summit.
The South African leader has been heavily criticised over the lack of progress in his mediation, a task handed to him by members of the 14-nation Southern African Development Community (SADC) last March.
A swift breakthrough in the talks would be a timely coup for Mbeki as he is hosting a SADC summit next month.