"Now is the time for finding common ground among Zimbabweans. Now is the time for flexibility, compromise and pragmatism," Arthur Mutambara, the leader of a small opposition faction, told reporters.
"As opposition we share and agree with the demands by the MDC-T," Tsvangirai’s main opposition group.
"We support those demands. We hope and trust Robert Mugabe and his party will be able to respond positively to the demands," said Mutambara.
Zimbabawe’s political rivals will meet South African President Kgalema Motlanthe, his predecessor Thabo Mbeki and Mozambican leader Armando Emilio Guebuza before negotiating teams iron out outstanding issues.
The three mediators are pushing for closure on a unity deal that stalled almost as soon as it was signed in September.
Mugabe and Tsvangirai have yet to agree on how to share power within cabinet despite repeated interventions by African leaders.
Mugabe threatened on Sunday to break off power-sharing talks if the opposition declined a deal, telling the government mouthpiece Sunday Mail newspaper "either they accept or it’s a break".
Tsvangirai’s Movement for Democratic Change (MDC) meanwhile, insisted it would not join a unity government until all its concerns had been addressed.
They include allegations that its supporters had been abducted and tortured by state security agents.
The impasse has only worsened the plight of ordinary Zimbabweans, with half the population dependent on food aid, astronomical levels of hyperinflation and a cholera epidemic sweeping unchecked across the country.