MDC leader Morgan Tsvangirai is supposed to become prime minister
Zimbabwe's opposition says it does not accept the outcome of a regional summit which said it should join a unity government next month.
The Movement for Democratic Change (MDC) said the meeting's conclusions "fell far short" of its expectations.
But President Robert Mugabe said an agreement had been reached and he hoped for a "new chapter" in relations.
As the arguments continue, more than 100 new cholera deaths have been reported in the past day.
Almost 3,000 people have died in the epidemic since August and more than 56,000 have been infected, the World Health Organization said on Tuesday.
'Pushing their luck'
Speaking at Harare airport on his return from the regional summit, Mr Mugabe said the parties had "agreed that an inclusive government should be formed" and that dates had been set for swearing in new ministers.
"We hope this will open up a new chapter in our political relations in the country and in structures of government," he said.
He said the concerns raised by the MDC over governorships and other appointments would be looked at.
SADC's POWER-SHARE TIMELINE
5 Feb: Zimbabwe to pass power-sharing constitutional amendment
11 Feb: PM-designate Tsvangirai and his deputies to be sworn in
13 Feb: Remaining ministers and their deputies to take office
Zimbabwe's deputy Information Minister Bright Matonga told the BBC there would be no more power-sharing talks.
Mr Matonga said: "There's not going to be any negotiations, I think that process has been done, it's concluded and the president [Robert Mugabe] will form a new cabinet.
"If they [the MDC] think they can hold Zimbabwe to ransom it will be very unfortunate. I don't think the people of Zimbabwe will allow that to happen. They [the MDC] are pushing their luck."
Mr Mugabe agreed to share power with MDC leader Morgan Tsvangirai last September but they have not been able to agree on how to allocate key government jobs.
After 14 hours of negotiations in Pretoria, the 15-nation Southern African Development Community (SADC) said the MDC had agreed to a timeline to form a unity government with Zimbabwe's Zanu-PF.
According to the timeline, a constitutional amendment would be passed to create the post of prime minister on 5 February, with Mr Tsvangirai being sworn in six days later.
South African President Kgalema Motlanthe said: "All the parties expressed confidence in the process and committed to implementing the agreement."
SADC leaders concluded that the contentious home affairs ministry, which runs the police, should be run jointly and reviewed six months after the new government was inaugurated.
Control over home affairs has been a key sticking point, with the MDC insisting it should run the ministry if Zanu-PF is to administer the defence and national security departments.
Hot on the heels of the SADC communique, an MDC statement said the party had not agreed to the deal, although it stopped short of rejecting the summit's conclusions outright.
It added that the party's national council would meet this weekend to define its position.
MDC spokesman Nelson Chamisa told the BBC: "Unfortunately our expectations were not met, our case was not received, in fact there was no objective understanding and assessment of the situation."
It was the fourth such meeting since the inconclusive elections last March.
The BBC's Peter Biles in Pretoria says SADC looks powerless and has shown no willingness to impose sanctions on Zimbabwe.
The country's state schools were supposed to open for a new term on Tuesday but the teachers' union said its members did not have the resources to get to work.
One teacher told the BBC that his monthly salary was only enough for a one-way trip to work, so he is selling maize meal instead.
The cholera outbreak has been fuelled by the collapse of the water, sanitation and health systems.
Nurses and doctors are also refusing to turn up for work.
Mr Mugabe and Mr Tsvangirai failed to resolve their differences during a meeting in Harare last week.
The MDC, along with Western nations, accuses Mr Mugabe of not being sincere about power-sharing, pointing to a spate of abductions of opposition officials and human rights activists.