After months of deadlock over the details of a power-sharing deal, Tsvangirai agreed on Friday to be sworn in as prime minister, and parties took the first steps to forming an inclusive government.
Both the United States and Britain were loathe to appear too optimistic over the advance, joining local critics who feel the implementation of the deal would show its success or failure.
"It brings hope on the surface that there may be better things to come and at the same time we remain sceptical," said Takavafira Zhou, a political scientist from the Masvingo State University.
"We have ideologically divergent groups forming a coalition," rather than a unity government, he said.
"The parties may remain rigid and pursue partisan rather than national interests. While there is hope we remain sceptical until the new government starts to deliver."
After almost a year since disputed polls which plunged Zimbabwe into a crisis, Southern African leaders gave leaders a strict timeline to form a new government which will see Tsvangirai sworn in on February 11.
"We are unequivocal, we will go into this government," said Tsvangirai.
"The SADC (Southern African Development Community) has decided and we are bound by that decision," he said after his party’s national council agreed it would go ahead with the unity government.
The crisis summit of a 15-nation bloc came as Zimbabwe battles an economic crisis which has seen inflation soar to over 231 million percent and a cholera epidemic that has left over 3 000 dead.
Both Britain and the United States, vehemently opposed to the regime of 84-year-old Mugabe, were restrained aver the future government.
"I’ve seen the reports about this agreement, but as you can understand, we are a bit skeptical. These types of things have been announced before," US State Department acting spokesperson Robert Wood said.
"The key is always implementation," he added.
Mugabe’s party has already said it accepts the SADC timeframe, and had previously threatened to set up a unity government with or without Tsvangirai.
An equally tempered reaction emerged from London, where British Foreign Secretary David Miliband said he looked forward to seeing details of a deal that would hold Zimbabwean lawmakers accountable.
"The new government will be judged on its actions, above all by the people of Zimbabwe," he said.
UN Secretary General Ban Ki-moon urged the new government "to take all necessary measures to address the humanitarian and economic crises in the country and respect democratic freedoms," his press office said in a statement.
The Southern African Development Community maintains that the power-sharing accord signed last September remains the best chance of pulling Zimbabwe out of its woeful state, but it has been held up by disputes over key posts.
"Zanu-PF has failed to deliver. The economic crisis is deeper, health and social support systems have collapsed and there is hope that the coming in of the MDC means better things may come. Donors may inject capital to revive the economy," said analyst Zhou.
Friday’s commitment to end the political stalemate was welcomed by South Africa, which came under intense global pressure to act on the crisis as chair of SADC and broker of the unity deal. – AFP