JOHANNESBURG — New mining in Zimbabwe has quickly yielded millions of carats of diamonds and could help catapult the nation into the ranks of the world’s top diamond producers, according to the head of a group of experts for the U.N.-backed effort to stop the trade in conflict diamonds.

But the new wealth has provoked fears that the riches will be used to subvert attempts to bring democracy to a country that has long suffered under authoritarian rule.

"This is a world-class deposit, no doubt about it," said the expert, Mark Van Bockstael. He described the concentrations of diamonds in the Marange fields in eastern Zimbabwe as among the highest in the world: "The deposit is a freak of nature."

Other experts agree it is an important find, while awaiting more data to gauge its full magnitude. But the steady accumulation of stones has already emboldened President Robert Mugabe, 86, to consolidate control over the Marange fields to prolong his 30-year grip on power, members of his inner circle said.

Although Mugabe now officially governs under a tenuous power-sharing agreement with longstanding rivals, the diamond fields are guarded by an army that reports to him and are overseen by a ministry run by his party, ZANU-PF, giving him and his allies lopsided control over a desperately needed economic boon.

"This is ZANU-PF’s salvation," said one of Mugabe’s closest confidants, on the condition of anonymity because his conversations with the president were supposed to be confidential. Diamonds are being sold on the black market for partisan and personal gain, he said, with some party leaders gaining and others being cut out: "The looting has intensified over the past six months."

Whether Zimbabwe will be able to sell the Marange diamonds on international markets as vetted stones that do not finance conflict faces a pivotal test this week. At a meeting that began Monday in Tel Aviv, the Kimberley Process — an effort by governments, the diamond industry and advocacy groups to stem the illicit diamond trade that has fueled wars in Angola, Sierra Leone and Congo — will consider whether the Marange diamonds should be cleared for export. More than 70 countries have committed not to trade with nations that do not meet the effort’s standards.

Investigators for both the Kimberley Process and human rights groups have reported evidence that the military used extreme violence in its 2008 operation to seize the Marange fields, employing dogs, AK-47s and even strafing from helicopters to attack miners who were part of a diamond rush. Officers then set up their own smuggling syndicates, the groups said.

"Nobody imagined that governments would be shooting their own people to get a grip on the diamonds," said Ian Smillie, an architect of the Kimberley Process.

Shallowly deposited by a river system, the stones are found in an area of about 265 square miles. Of that, some 46 square miles are thought to have diamond potential.

Van Bockstael estimated that only 5 percent of the stones found are of gem quality, while some 90 percent are of low quality, useful only for industrial purposes. They look like pebbles or chips of broken beer bottles, tinted black, brown or green.

"If you found one on the street, you probably wouldn’t even pick it up," he said.

Late last year, two companies in joint ventures with the state-owned mining company began mining Marange concessions and had already amassed 4.4 million carats of diamonds by May.

Van Bockstael, a geologist, says he is waiting for Zimbabwe’s promised geological report on the fields. But from interviews with officials and other data, he says they could yield $1 billion to $1.7 billion a year, earnings that would put Zimbabwe in the world’s top half-dozen diamond producers.

Those are huge sums for a country whose gross domestic product was only $4.4 billion in 2009, according to the International Monetary Fund. Zimbabwe sorely needs new money to combat hunger, disease and poverty.

Some questioned the fields after De Beers, the mining giant, let its Marange concession lapse in 2006. But Andrew Bone, the company’s director of international relations, described the diamonds there as "an important find. It’s bigger than most people anticipated."

Bone said De Beers was worried about the country’s worsening political crisis when it withdrew.

"We didn’t perhaps do as much surveying as we could have done," he said.

Others in the industry are taking the deposits seriously. Ernest Blom, chairman of the Diamond Dealers Club of South Africa, said it contained mostly low-quality diamonds but "yielding enormous carats per ton. It’s huge."

Views on whether Zimbabwe should be certified to sell its diamonds are polarized. Mugabe has depicted efforts to block the country from diamond trading as part of a Western plot to topple him. Officials in his party deny all accusations of state-sponsored violence against miners and say the government has met the required international standards, properly securing its diamond fields.

Advocacy groups that are part of the Kimberley Process disagree, saying Zimbabwe should be suspended for continuing human rights violations.

But this month, Abbey Chikane, a South African businessman assigned by the Kimberley Process to monitor the Marange fields, recommended that the diamonds be certified and that the military continue guarding the fields until the police — also answerable to Mugabe — can take over.

"The government of Zimbabwe has demonstrated its commitment to meet the minimum requirements," Chikane wrote in his confidential report to the Kimberley Process, which was provided to The New York Times by a participant. "A great deal of hard work has gone into their efforts."

The Zimbabwe case poses challenges to the Kimberley Process itself. Its mission is defined as stemming the trade in conflict diamonds used to finance rebel movements. But in Zimbabwe, elements of the government itself have been accused of violence against ordinary people who flooded the Marange fields to sift for stones during a diamond rush that began in 2006.

The deliberations are likely to be contentious. Farai Maguwu, the most outspoken Zimbabwean advocate on diamond issues, was supposed to attend the meeting in Tel Aviv but is instead jailed in Harare after providing information to Chikane.

Analysts and civic leaders fear that rather than bringing hope for Zimbabwe’s long-suffering people, this new wealth will reinforce authoritarian rule. They say it could finance more of the patronage and repression that have kept Mugabe in power, and possibly infect the Movement for Democratic Change, the junior partner in the power-sharing government, with what Eldred Masunungure, a political scientist at the University of Zimbabwe, called "the predatory virus."

"The gravy train is not likely to be one that leads to a democratic destination," Masunungure said.