The deal, brokered by Mbeki last month, is in danger of collapse over disagreements about cabinet posts and Tsvangirai, leader of the MDC, threatened to pull out of it at the weekend after Mugabe allocated key ministries to his ZANU-PF party.
Mutambara expressed frustration over the stalled deal.
"The fact that we are here, bickering over cabinet posts is a travesty of justice. Mutambara, Mugabe and Tsvangirai should shape up or ship out," he told reporters as he arrived.
Justice minister and ZANU-PF’s chief negotiator in the power-sharing talks, Patrick Chinamasa, told the state-run Herald that he hoped Mbeki could offer new ideas.
"As far as we are concerned, the only contention is the Ministry of Finance," he said. Mugabe this weekend angered the MDC by allocating the ministries for defence, home affairs — which oversees the police — and finance to his ZANU-PF party.
On Tuesday, Zimbabwe’s parliament began sitting for the first time since it was officially opened by Mugabe in August amid jeers and boos from MDC members.
Mugabe’s party was stripped of a majority for the first time since independence from Britain in 1980 after a March 29 election which the opposition says he rigged to retain power.
Tsvangirai defeated Mugabe in a March presidential poll held concurrently. But he did not have enough ballots to avoid a June run-off poll, which was won by Mugabe and condemned around the world after it was boycotted by Tsvangirai.
Sharp differences were evident in parliament, with ZANU-PF lawmakers praising Mugabe for agreeing to share power, while their MDC counterparts said they could walk away from the deal.
"If we are genuine … we should share power equitably. It cannot be an inclusive government at any cost," said MDC lawmaker Sam Sipepa Nkomo. "We can’t be swallowed and we should not allow ourselves to be lipstick on ZANU-PF, a decoration."
Lawmakers are expected to prioritise a constitutional amendment allowing the creation of the prime minister’s post, which the power-sharing deal agreed would be filled by Tsvangirai.
Nelson Chamisa, an MDC spokesman, said he hoped Mbeki would break the cabinet impasse.
"We are still placing our faith in the efforts of the mediator, and that ZANU-PF has to be persuaded that it has to share and not grab power," he said.
Analysts say that although the talks look doomed, the rivals are under pressure to reach a settlement, although some say Mbeki will have less leverage in Zimbabwe after being ousted as South African president by his own party last month.
A new government will have to tackle the world’s highest inflation rate of 231 million percent and severe food, fuel and foreign currency shortages. Reuters