Mines Minister Obert Mpofu, a Mugabe-appointed minister, insists that Western economic sanctions have prevented the government from getting fair prices for the diamonds on the international market and forced some covert selling.

Zimbabwe is said to have the capacity to produce between 110 million to 160 million carats of diamonds annually, ranking it as one of the top five diamond producers by volume in the world.

An international diamond watchdog, Partnership Africa Canada alleged last year that at least $2 billion have been stolen by Mugabe's cronies from Zimbabwe's eastern diamond fields.

It said the vast earnings could have turned around Zimbabwe's economy, crippled by years of economic meltdown and political turmoil.

"We can't have a government which is indifferent to the costs of a referendum and elections," Biti said.

He said funding for Saturday's referendum has been raised from a giant local real estate and pension fund enterprise and other private interests as well as the sale of government treasury bills.

Zimbabweans are to cast their votes in the referendum at 9,000 voting stations countrywide Saturday. All political leaders have called for a 'Yes' vote from their supporters to accept a new constitution.

Crucial national elections are expected to be sometime in July, with Tsvangirai, 61, running against Mugabe, 89, in the presidential poll.

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