PM Tsvangirai withdrew from government three weeks ago
Zimbabwean Prime Minister Morgan Tsvangirai has called off his party's boycott of the unity government with President Robert Mugabe.
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 regional crisis talks in Mozambique.
The MDC accuses Mr Mugabe's Zanu-PF of continuing to harass its activists and acting in "bad faith".
The Southern Africa Development Community (Sadc), which is the guarantor of last year's power-sharing agreement, urged all parties to respect the deal and said they had 15-30 days to "engage in dialogue".
By Karen Allen, BBC News, Johannesburg
The meeting in Maputo is not offering a magic bullet. The parties have the next 15-30 days to "engage in dialogue".
The MDC has interpreted that to mean that a clear timetable is to be set for the swearing-in of governors and its nominee for deputy agriculture minister - Roy Bennett. It also expects its partner in government to address other outstanding issues of the global political agreement, in particular the appointment of the governor of the central bank and the attorney general.
But what if that does not happen, what are the sanctions available?
The MDC has taken some solace that South Africa's President Jacob Zuma has promised to take stock of the situation in 30 days' time. But there has been little sign of the "more vocal" stance President Zuma's ANC party has promised on Zimbabwe.
Mr Tsvangirai's Movement for Democratic Change says outstanding issues should be agreed within 15 days and thenimplemented within 30 days.
Mr Mugabe did not speak to the media after the summit.
Mozambican President Armando Guebuza said he thought the situation would change within 30 days.
Sadc head Tomaz Salomao said South Africa's President Jacob Zuma would soon visit Zimbabwe to evaluate progress.
The next Zimbabwe cabinet meeting is on Tuesday, and MDC spokesman Nelson Chamisa said his party's ministers would attend.
Mr Tsvangirai walked out of the coalition government on 16 October in protest at the detention of a senior MDC official on terrorism charges and over Mr Mugabe's failure to implement political agreements.
The official, Roy Bennett, was later released on bail and is due to go on trial on Monday on charges of terrorism, insurgency, sabotage and banditry.
He was arrested in February, as he was due to be sworn in as deputy agriculture minister.
MDC accuses Zanu-PF of campaign of violence, Zanu-PF dismisses claims as 'outrageous'
MDC says central bank governor and attorney general must be replaced, Zanu-PF disagrees
MDC says terrorism charges against him should be dropped, Zanu-PF says courts must decide
Mr Mugabe refuses to swear in MDC nominees
MDC says farm seizures must stop, Zanu-PF disagrees
The MDC also said there had been "increased violent" attacks on party members by militants from President Mugabe's Zanu-PF, as well as renewed invasions of white-owned farms.
Last week, Zanu-PF described the allegations as "cheap propaganda".
Mr Tsvangirai's allies also accuse Mr Mugabe of making key appointments, such as the attorney general, the central bank governor, provincial governors and diplomats, without consulting them.
Zanu-PF says the MDC has not done enough to attract foreign aid and investment since it joined the government to end the impasse following last year's disputed elections.
The unity government has managed to halt Zimbabwe's economic collapse but donors remain wary of resuming funding.