The removal of Gideon Gono, 48, a key ally of President Robert Mugabe, is "one of the key indices" that western governments will use to judge whether the newly constituted government is genuinely reformed and a fit recipient for aid, the official said.
As the controller of Zimbabwe’s finances since 2003, Mr Gono has played a key role in shoring up the edifice of the ruling Zanu-PF party and Mr Mugabe’s own position, printing ever more cash to meet the government’s needs.
The policy has been one of the main drivers of the country’s hyperinflation, officially over 11.2 million per cent but estimated by independent analysts to be far higher. This week he effectively abandoned the currency, legalising the partial dollarisation of the economy in a move seen in some quarters as an attempt to preserve his power base.
The diplomat said that Mr Gono had "less than zero" credibility and while the international community has offered billions in aid to a reforming Zimbabwe, it was essential that the power-sharing deal agreed last week must first be seen to work.
Under the deal, details of which are to be announced tomorrow, Mr Mugabe remains president with Morgan Tsvangirai, the Movement for Democratic Change leader, becoming prime minister.
An expectation that the foreign aid tap would be turned back on to help the country recover from its current economic chaos was one of the most powerful pressures that forced Mr Mugabe finally to share power with Mr Tsvangerai.
Asked if Mr Gono’s sacking was a necessary step before aid was released, the diplomat said: "Everyone knows it is. It’s one of the key indices. Tsvangirai has said it is one of the first things he will do, if he doesn’t flee the country first."
He added that Mr Gono, whose term of office expires in November, should go within two weeks. It is understood that under the terms of the power-sharing agreement, appointments to such senior posts must in future be made jointly by the president and the prime minister.
With the world waiting to see the exact nuts and bolts of the power-sharing deal, the diplomat’s comments reveal one of the yardsticks that will be used to judge it in Western capitals.
"There is very little time left for the country as a going concern," he said. "If this government is going to have any momentum it needs to start doing things early. Tsvangirai is keen to get going with the beginnings of stabilising the economy and unless that happens he will not have the confidence of donors.
"If that doesn’t happen it’s a lost chance and the chance is gone because with it would have gone Tsvangirai’s credibility."
Diplomats estimate that around $2 bn could be poured into Zimbabwe in the new government’s first year, with more to come later, from the IMF, World Bank, and individual Western countries.
Under the power-sharing deal, sources have said that a council of ministers, chaired by Mr Tsvangirai and including all ministers except Mr Mugabe and his two vice-presidents, will set government policy and strategy, while the cabinet, chaired by the octogenarian president, will oversee its implementation.
Opinion remains divided, with optimists saying Mr Tsvangirai has a key position in government, but pessimists concerned that Mr Mugabe will out-manoeuvre him despite his office.
"Mugabe sees this as a kind of unity deal from 1987, when he devoured Nkomo," said the diplomat. "Few people think Zanu-PF are going into this in good faith.
"But this is not 1987, the regime has never been weaker, the country is on its knees, the economy is disintegrating before our very eyes. There’s more to play for than many of the cynics would admit, but it’s touch and go."
On the streets of Harare the mood was cautious. "We are waiting to see what the deal really is," said one businessman. "I think it can work. It has to, we are so poor."
One potential problem for the prospects of a power-sharing government is hostility from Mr Mugabe’s henchmen. Army and secret police chiefs fear they could lose the fortunes they have accumulated under Mr Mugabe’s corrupt rule, including formerly white farms which have been confiscated and mines that they now own.
Mr Mugabe’s lieutenants have become some of the richest and most powerful men in the country, regarded by many as the real power.
They harbour a personal hatred of Mr Tsvangirai. One senior official with the Central Intelligence Organisation said: "The bosses will either have to ship out, or salute Tsvangirai. There is a general belief that most of the big guys will resign to make way for a new dispensation. The bosses are threatened by the deal because most of them have many properties and they are afraid of what may happen to them." The Telegraph (UK)