"We have gone past negotiations and whatever concessions were there to be made have already been made."
Monday's talks will be the first meeting between Mugabe and Tsvangirai since November 9.
Kgalema Motlanthe, the South African president; his predecessor Thabo Mbeki; and Armando Emilio Guebuza, the Mozambican president, will mediate the discussions.
A Sunday Mail editorial said that Mugabe could form a government with his Zanu-PF party, leaving out Tsvangirai if no deal is reached.
"SADC [the Southern African Development Community] must be prepared to live with the possibility that a government may have to be constituted without the MDC formations. Zimbabwe cannot remain in limbo forever," it said.
The MDC had said that it would insist on its demands being addressed during negotiations, including allegations that its supporters have been abducted and tortured by state security agents.
"The position that has been reiterated is that all outstanding issues should be resolved before an inclusive government comes into place," Nelson Chamisa, the MDC spokesman, said.
"The leadership has been given the mandate to finalise the talks tomorrow either in success or in failure, so that there is finality to this very protracted phase of negotiations."
Chamisa said that his party should have more leverage because it won a first election in March.
The MDC won initial parliamentary elections in March which precipitated widespread political violence. An uncontested presidential run-off then took place in June in which Mugabe was victorious.
A power-sharing deal was originally signed by both sides on September 15, but has not come into force.
It places Mugabe as president while Morgan Tsvangirai, the MDC leader, would take the new post of prime minister. But disputes have continued as to how power should be shared within the cabinet in the deal.
The failure to find agreement has exacerbated a worsening humanitarian situation in Zimbabwe, where more than half the 11 million population is dependent on food aid.
A cholera epidemic has spread thorught the country, and the UN has said that Mugabe has not done enough to assist humanitarian supplies.
The UN estimates that more than 1,500 cases of cholera are occurring every day.