The international body that tries to prevent the trade in so-called blood diamonds has failed to take a decision about whether Zimbabwe's stones should be certified as conflict free.
Diamond mining has become a lucrative business in Zimbabwe, with government officials estimating that the trade could earn the country $1.2bn per month.
The Kimberly Process, an international certification body, was supposed to finish meetings in Tel Aviv, Israel, on Wednesday.
But the group - made up of diamond exporters, a collection of some 70 countries and rights monitors - was unable to come to an agreement on Zimbabwe.
At the end of Wednesday's meetings, Boaz Hirsch, the Kimberly Process chairperson, said: "There has been quite a lively discussion with a whole spectrum of opinions expressed."
Human Rights Watch (HRW) accuses President Robert Mugabe of sending troops the into the Marange fields, in eastern Zimbabwe, to gain control of the resource in a campaign of "torture, beatings and harassment".
'Life is hell'
One "community leader" in the mining area told HRW that "soldiers routinely force us to mine for diamonds. If anyone refuses, they are tortured. Life in Marange is hell".
Mark Van Bockstael, an expert on diamonds, has called the Marange fields a "world class deposit" and a "freak of nature".
Abbey Chikane, the South African monitor appointed to investigate conditions in the area, has recommended the certification of Zimbabwe's diamonds, as they have met "minimum conditions".
Mineral exports, if managed properly, could lift thousands out of poverty in a country whose gross domestic product was only $4.4bn in 2009.
Obert Moses Mpofu, Zimbabwe's minister of mines and mining development, told Kimberly Process delegates that his country "will be contributing more than 30 per cent of the diamonds produced in the world".
Critics say the wealth will be siphoned off by allies of Mugabe's ruling Zanu-PF party, which has been accused of crushing opponents and destroying the country's economy.
"This is Zanu-PF’s salvation," one of Mugabe's closest confidants told the New York Times.
He alleged that senior party members have been selling diamonds on the black market.
"The looting has intensified over the past six months," he said.
Zanu-PF is currently sharing state power with longstanding rivals in an internationally backed coalition government, but critics say Mugabe's allies in the military are controlling the mines.
The Kimberly Process was created a decade ago, after battles over diamond mines among various rebel groups financed brutal civil wars in west Africa, Sierra Leone in particular.