A South African businessman accused of threatening to unleash biological weapons on Britain and the United States may have been driven by concern over the plight of white farmers in neighboring Zimbabwe, a spokesman for the prosecution said Monday.

The suspect, Brian Roach, did not have the means to carry out his threats to spread foot and mouth disease, spokesman Mthunzi Mhaga said. The 64-year-old Roach, who owns an engineering firm outside Johannesburg, appeared in a Johannesburg court Monday after his arrest Saturday on terror charges.

Roach threatened in letters and e-mails sent to the British government to spread the disease in Britain and the United States unless he was given $4 million.

"We have the expertise and resources to do this very effectively and will be able to devastate the industry in the U.K. which will cost billions to the economy," Roach wrote in an e-mail to the British government. "We will devastate your farms and then we will then take the problem to your coconspirator the USA."

Roach appeared to believe the U.S. and Britain should do more to help white Zimbabwean farmers, Mhaga said. About 4,000 white farmers have been forced from their farms since 2000 in what Zimbabwean President Robert Mugabe calls a campaign to put more land in the hands of impoverished blacks. Many of the beneficiaries, though, have been top politicians who are close to Mugabe.

Roach said he wanted compensation for losses incurred by Zimbabweans because of the U.S., which he said influenced the situation in Zimbabwe with only its "own interest at heart."

On Oct. 6, Roach wrote in an e-mail: "We are not habitual criminals but have been victim of a situation which was entirely out of our control and attributed to corrupt and incompetent politicians."

Violence in Zimbabwe has surged since January, when Mugabe called for elections later this year to bring Zimbabwe's troubled coalition to an end. The power-sharing government — a joint coalition of Mugabe and Morgan Tsvangirai, the formal opposition leader — took office Feb. 11, 2009 after disputed elections plagued by violence and allegations of vote rigging in 2008.

South African police said a six-month terror investigation by South African, British and U.S. officials culminated with Roach's arrest. U.S. and British officials confirmed they had worked closely with the South Africans.

"This biological agent, if deployed, would have caused the destruction of property and resulted in major economic loss," a South African police statement said. "This was therefore regarded as a very serious threat."

Police charged Roach with terrorist activity and money laundering. The gray-haired man, married with four grown children, appeared briefly in court Monday, wearing glasses and a black fleece jacket.

Police said Roach made the threats repeatedly in letters and e-mails sent from Internet cafes. Police searched Roach's home and other sites, but found no evidence he would have been capable of carrying out his threats.