Movement for Democratic Change leader Tsvangirai and Mugabe are both under pressure to resolve their differences about the make-up of a government of national unity and begin working together to address the country’s economic and humanitarian crisis.
The United Nations said earlier that the number of deaths in a cholera outbreak since August had risen sharply in recent days to 746.
"We do appreciate that we are in a serious crisis," Tsvangirai said in a BBC interview. But he placed the matter firmly at Mugabe’s feet: "Mugabe must realise he is responsible for this crisis."
Tsvangirai denied that he was avoiding joining a proposed unity government in the hope that Mugabe would resign. A number of Western and African leaders have, about the past week, renewed their calls for the elderly leader to quit.
"The African leadership’s call for him to go is nothing new," Tsvangirai said, calling for "action" over words alone.
At the same time, he said, "We believe that the global political agreement (the power-sharing deal that he and Mugabe signed in September) laid the basis for further negotiations but there are still outstanding issues that need to be hammered out."
Among the sticking points are the sharing of key cabinet posts, particularly the home affairs ministry that controls the police. The MDC says it should run that ministry given the history of state violence against its members. Mugabe’s Zanu-PF is insisting on shared control.
The MDC’s distrust of Zanu-PF has been deepened by a new campaign of repression and intimidation against the opposition and activists.
Tsvangirai held Mugabe personally responsible for the fate of a group of around 19 missing MDC members and activists.
"As far as we are concerned Mr Mugabe is responsible for upholding the law….The fate of those people, whether dead or alive, is in his hands." – Sapa-dpa