Updated

Expressing confidence in the safety of Canadian beef, the Bush administration said Thursday it would stand by its decision to renew Canadian cattle imports beginning in March despite a possible new case of mad cow (search) disease.

The Agriculture Department (search) said that even if the Canadian cow is confirmed positive for mad cow disease it believes public health measures in Canada and the United States will protect U.S. livestock and consumers.

"Because of the mitigation measures that Canada has in place, we continue to believe the risk is minimal," said Ron DeHaven, administrator of the department's Animal and Plant Health Inspection Service.

A day after the United States announced that with some restrictions it would reopen its borders to Canadian live cattle, the Canadian government on Thursday announced it may have another case of mad cow disease. It said preliminary screening of a "downer" cow — one unable to walk — showed multiple positive results for mad cow.

Definitive tests have yet to be completed, Canadian officials said.

The decision to allow Canadian cows into the United States in light of the latest potential mad cow concern brought sharp responses from several Democratic lawmakers.

Rep. Earl Pomeroy, D-N.D., called the decision "outrageous" and accused the Agriculture Department leadership of caring "more about the interests of mega feed lots and processors than the interests of farmers, ranchers and consumers."

Sen. Byron Dorgan (search), D-N.D., said he wanted to know if the Agriculture Department knew Canadian officials were investigating a suspected case of the disease when they decided to declare Canadian beef a "minimal risk."

North Dakota's other Democratic senator, Kent Conrad, said that even in the absence of the latest mad cow scare, he opposes the administration's decision to renew importation of Canadian cattle.

"I am not persuaded that Canada has taken all the steps necessary to prevent additional outbreaks there," Conrad said in a telephone interview.

In a letter sent Thursday to Agriculture Secretary Ann Veneman (search), Conrad urged that the border stay closed to Canadian beef.

U.S. imports of Canadian beef and cattle were halted 19 months ago after a case of mad cow disease was discovered in Alberta, Canada. Concerns persisted after a Canadian-born cow in Washington state was found in December 2003 to have mad cow disease, formally known as bovine spongiform encephalopathy, or BSE. The disease attacks an animal's nervous system, and food contaminated with BSE can afflict people with Creutzfeldt-Jakob disease, which is usually fatal.

The Canadian Food Inspection Agency released few details about the cow suspected of being infected except to say it was a 10-year-old dairy cow in northern Alberta and that no parts of the animal had entered the human food or animal feed system.

DeHaven said Canadian officials informed the U.S. government Wednesday night, only hours after the USDA had announced plans to resume imports of Canadian beef, beginning in March.

"If this animal proves to be positive, it would not alter the implementation of the U.S. rule ... that recognizes Canada as a minimum-risk region," said DeHaven, adding that in deciding to resume imports the agency had considered the possibility of additional cases of mad cow disease being found in Canada.

DeHaven said beef brought into the United State will be subject to Canadian inspection and subject to re-inspection by the USDA Food Safety and Inspection Service.

The USDA ruling, effective March 7, declares Canada a "minimal-risk region" so that cattle could be shipped into the United States under certain restrictions. The cattle must be slaughtered by the age of 30 months, which scientists say is too young to contract mad cow disease, and they must also be transported in sealed containers to a feedlot or slaughter house.

"After conducting an extensive review, we are confident that imports of certain commodities from regions of minimal risk can occur with virtually no risk to human or animal health," Veneman said when the ruling was announced.

The discovery in Washington state a year ago is the only confirmed case of mad cow disease in the United States. There have been a handful of suspected mad cow cases during preliminary screening in the United States, but more sophisticated tests produced negative results for the disease.

Both the beef industry and the USDA acknowledge that eventually another mad cow case is likely to be discovered among the 40 million adult cattle in the United States. About 1 percent of the herd, or 446,000 cattle, are considered in the targeted "high risk" category, according to the USDA, because they are not ambulatory and do not show signs of other ailments.