The two rivals are supposed to share power equally
Zimbabwean President Robert Mugabe has told his party's leaders that Monday's power-sharing deal is a "humiliation".
But he said the party had no alternative after losing the March parliamentary elections.
Mr Mugabe is expected to meet prime minister-designate Morgan Tsvangirai later to discuss allocating ministerial posts under the deal.
Correspondents say there is intense lobbying for positions among all the parties involved in the agreement.
Under the deal, Mr Mugabe's Zanu-PF has 15 posts in cabinet, Mr Tsvangirai's Movement for Democratic Change (MDC) 13 and a smaller MDC faction three.
But the allocation of portfolios among the parties and the naming of the ministers has still to be decided.
Meanwhile, the international Red Cross is to start distributing food aid shortly.
Trucks carrying some 383 tonnes of aid travelled through the night after loading supplies in Harare, Bulawayo and Mutare.
The food will be handed out to about 24,000 people.
Red Cross spokesman Matthew Cochrane told the BBC that some two million people need food aid, and this could rise to five million - half the population - by the end of the year.
"The situation is critical," he said.
Who's in charge?
A meeting between Mr Mugabe, Mr Tsvangirai and faction leader Arthur Mutumbara to discuss the distribution of cabinet posts has been postponed since Tuesday.
But Mr Mugabe's former Justice Minister, Patrick Chinamasa, told state TV that the meeting would take place on Thursday and a new cabinet could be decided on by the end of the day.
Mr Mugabe told a meeting of Zanu-PF's leadership ahead of the meeting:
The new government's first priority is to revive the economy
"If only we had not blundered in the March... elections we wouldn't be facing this humiliation.
"This is what we have to deal with."
But he nevertheless said Zanu-PF remained "in the driving seat".
"We are still in a dominant position which will enable us to gather more strength as we move into the future," he said, according to the state-run Herald newspaper.
The deal is intended to share power equally but correspondents say it is unclear if either party has the upper hand.
Under the deal, Mr Mugabe will chair the cabinet, while Mr Tsvangirai will chair a "council of ministers" attended by all cabinet ministers.
The cabinet under Mr Mugabe will decide on government policy, while the council of ministers will implement it.
Mr Chinamasa said the cabinet would meet each week, while the council of ministers would meet quarterly.
Analysts fear the arrangements could lead to rival centres of power being formed.
But Mr Tsvangirai told the BBC this would not be the case.
"We have to make sure that doesn't happen," he said.
"I am confident we will be able to deliver."
The new government's first priority is to try to revive the ruined economy.
Annual inflation is running at an official rate of 11,000,000% and just one adult in five has a regular job. Up to half the population will need food aid by the end of the year, donors say.