"Through a sophisticated web of companies, Bredenkamp has financially propped up the regime and provided other support to a number of its high-ranking officials. He also has financed and provided logistical support to a number of Zimbabwean parastatal entities."
A representative for Bredenkamp said that he "vehemently denies all these charges," adding, "Mr. Bredenkamp has not met Mr. Mugabe for over 23 years. Neither is he a close associate of any minister or Zanu-PF official." And, the representative said, the company is challenging the U.S. Treasury Department designation.
Zimbabwean Muller Rautenbach, another businessman blacklisted by the U.S. Treasury, is a shareholder in the Central African Mining and Exploration Co., or CAMEC, which loaned Mugabe's government $100 million.
In an e-mail to ABC News, CAMEC spokesman Jon Simmons said that the company loaned the money so that the government could make its "payments to a series of mainly international creditors for a variety of commodities, primarily for seeds, grain, fertilizer and fuel."
"CAMEC undertook appropriate due diligence, as a result of which it is satisfied that the payments were used for these purposes. CAMEC has no reason to believe that the money may have been used for other purposes and has seen no evidence to suggest that this may be the case."
Garwood of the World Health Organization told ABC News that Zimbabwe is now in serious danger of facing more serious health risks because hunger and malnutrition are on the rise.
"There are great challenges with access to food in many parts of the country," he said. "By having people malnourished it just accentuates risks of increases of various diseases and makes people more prone to instances of cholera."
Even though Zimbabwe has modern hospitals and well-trained doctors, according to Garwood, the meager wages given to health workers have meant a virtual shutdown of these facilities as many workers search for other ways to bring in food.
Similarly, Zimbabwe -- once known as Africa's breadbasket -- now struggles to feed its own in the aftermath of years of inflation.
Mugabe has ruled the country since its 1980 independence from Britain.
Critics blame his policies for the ruin of the once-productive nation, while Mugabe blames Western sanctions for the country's meltdown.
Opposition leader Tsvangirai said Friday that he intends to ask his party, the Movement for Democratic Change, to halt negotiations unless political detainees are released or charged by Jan. 1.
He told reporters in Botswana that more than 42 members of his opposition party and civil society had been abducted in the last two months. They include three journalists; their whereabouts remain unknown.
"The MDC can no longer sit at the same negotiating table with a party that is abducting our members and other innocent civilians and refusing to produce any of them before a court of law," Tsvangirai said.
Donna Sherrington, The Associated Press and Reuters contributed to this story.