Mugabe signed the agreement with Tsvangirai on Monday, relinquishing some powers for the first time in nearly three decades of rule under pressure from regional leaders and a growing economic crisis.
"The meeting was inconclusive, it was a deadlock and has been referred to the negotiating teams for further work to try and find common ground," said Movement for Democratic Change spokesman Nelson Chamisa.
The state-run Herald newspaper said earlier Mugabe had told a meeting of his ZANU-PF party on Wednesday that the agreement was "a humiliation".
"Anyhow here we are, still in a dominant position which will enable us to gather more strength as we move into the future. We remain in the driving seat," Mugabe said.
The deal with Tsvangirai and the head of a breakaway opposition faction followed weeks of tense negotiations to end a political crisis compounded by the veteran leader’s disputed and unopposed re-election in a widely condemned vote in June.
Under the agreement, Tsvangirai, who heads the largest of the two MDC factions, will become prime minister and chair a council of ministers supervising the cabinet.
Tsvangirai’s party is expected to get 13 cabinet posts, with Arthur Mutambara’s breakaway faction likely to control an additional three ministries.
Mugabe’s ZANU-PF, which lost control of parliament in the March election for the first time in 28 years, is likely to have 15 ministers in the cabinet.
But the 84-year-old Zimbabwean ruler, who has governed since independence from Britain in 1980, will retain the presidency and head the cabinet as well as keep control of the powerful army. The police are expected to fall under the opposition.
Zimbabweans hope the agreement, brokered by South African President Thabo Mbeki, will be a first step in helping to rescue the once prosperous nation from economic collapse.
Inflation has rocketed to over 11 million percent and millions have fled to neighbouring southern African countries.
Western nations and international agencies have said they will be ready to help the new government financially if it commits itself to political and economic reforms and shows a clear commitment to tackle the crisis.
Members of the Southern African Development Community, a 15-nation regional body, will also have to make a financial contribution to rebuilding Zimbabwe’s economy, South African government spokesman Themba Maseko told reporters in Pretoria.
South Africa has set up a task force to develop an emergency intervention plan that will largely focus on reviving Zimbabwe’s once prosperous agricultural sector, Mbeki’s cabinet announced on Thursday.