Robert Mugabe, the Zimbabwean president, has unilaterally allocated key ministries to his own party members in defiance of a power-sharing deal, reports say.
The rival Movement for Democratic Change (MDC) has reacted with outrage and said on Saturday that Mugabe's action "jeopardised" the agreement signed last month.
The parties have been deadlocked in allocating ministries and have called back South African mediators.
Thabo Mbeki, the former South African president, brokered the initial deal between the MDC and Mugabe's Zanu-PF.
The power-sharing agreement was signed in September, but since then the rival parties have been unable to reach an agreement on cabinet posts.
Under the agreement brokered by Mbeki, Mugabe remains the president while Morgan Tsvangirai, the leader of MDC, takes the new post of prime minister.
But efforts to form the government have bogged down over disputes about who will control the most important ministries, such as defence, home affairs and finance.
Citing a government gazette, a list published in The Herald newspaper gave Mugabe's party 14 ministries including the portfolios of defence, home and foreign affairs and justice as well as local government and media.
Tsvangirai's MDC has been allocated 13 ministries, among them constitutional and parliamentary affairs, economic planning and investment promotion, labour and social welfare, sport, arts and culture and science and technology development.
A splinter opposition grouping led by Arthur Mutambara will be in charge of education, regional integration and international co-operation and industry and commerce, the report added.
Reacting to the announcement, an MDC spokesman said that the September 15 deal on power-sharing was in "jeopardy".
"What we are seeing is arrogance on the part of Zanu-PF which will put the deal into jeopardy," Nelson Chamisa said.
Chamisa said Tsvangirai would not sign up to such a government.
"That list does not and will not have the endorsement of the MDC. This is unilateral, contemptuous and outrageous."
State media said on Thursday that Zimbabwe's inflation rate had soared to 231 million per cent in July - the highest in the world.
The United Nations estimates that nearly half of the population will need food aid, with 80 per cent of the population living in poverty.