Mr Tsvangirai said he was giving Mr Mugabe 30 days to implement the power-sharing agreement on "the pertinent issues we are concerned about".
The prime minister was speaking after a regional summit in Mozambique.
Mr Tsvangirai and his Movement for Democratic Change party boycotted the government on 16 October.
Four heads of state from the regional grouping have been meeting in the Mozambique capital Maputo to end the stalemate in the Zimbabwe government which has threatened to see the country plunge further into crisis.
Regional mediators the Southern Africa Development Community (SADC), which is the guarantor of last year's power-sharing agreement, have instructed the parties that they have 15 days to resolve outstanding issues.
The next Zimbabwe cabinet meeting is on Tuesday, and the MDC spokesman, Nelson Chamisa, said his party's ministers would attend.
Mr Tsvangirai walked out of a coalition government in protest at the detention of a senior MDC aide on terrorism charges and over Mr Mugabe's failure to implement political agreements.
The aide, Roy Bennett, was later released on bail.
The MDC also said there had been "increased violent" attacks on party members by militants from President Mugabe's Zanu-PF.
Zanu-PF described the comments, on 27 October, as "cheap propaganda" following the MDC's decision to end co-operation.