Spokesman Nelson Chamisa said the Movement for Democratic Change and Mugabe’s ZANU-PF were "worlds apart" after the two leaders met to try to resolve the crisis.
"If they (Mugabe and his ZANU-PF) are facing west we are facing east," Chamisa said.
The crisis hit the fragile coalition earlier this month when the MDC said it would stop attending cabinet meetings in protest against the arrest of one of its senior officials and Mugabe’s refusal fully to implement a political agreement.
Mugabe and his old foe Tsvangirai entered the unity government after disputed elections left the impoverished African state in a stalemate and in danger of serious violence.
¦Difficulties in implementing their agreement have delayed efforts to secure billions of dollars from Western donors, money that is crucial for Zimbabwe’s economic recovery.
Chamisa said the MDC would now wait for the outcome of mediation by the Southern African Development Community (SADC), and if this failed to end the deadlock the party would start to prepare for elections.
"If that (mediation) fails, unfortunately we have to start to prepare for elections because there is no government without the GPA (Global Political Agreement)," Chamisa told Reuters.