The designation would hinge on whether the infected cow was imported, as early evidence suggests.
Scientists are expected to report early next week if the infected Holstein milk cow in Washington state was born in Canada, based on two separate DNA tests.
Two dozen nations stopped importing US beef following the discovery. To reassure international and domestic consumers, the Bush administration announced new safeguards, including a ban on butchering sick or injured cattle for human food.
"We have the opportunity to preserve our export market," said Michael Stumo of the Organisation for Competitive Markets, a group that supports small farmers.
It wants the Bush administration to declare the United States "provisionally free" of mad cow, also called bovine spongiform encephalopathy.
"That's the whole reason for the losses," he said.
Standards set by the World Organisation for Animal Health say a nation can be classified as provisionally free of mad cow when the disease is found in imported cattle and authorities are diligent in rooting it out and in maintaining safeguards.
"As you know, we are just one week into the investigation so it is too early to say what actions we will be taking in regard to OIE status," an Agriculture Department spokeswoman told Reuters, using the French abbreviation for the animal health organisation.
That approach would jeopardise the administration's credibility, consumer groups said.
"It would not be a good interpretation from a public health standpoint" nor one that Americans would believe, said Caroline Smith DeWaal, food safety director of the Centre for Science in the Public Interest, a consumer group.
Canada and the United States have a large cattle trade, DeWaal said, so blaming Canada would not end the need for US caution. Canada reported its first native case of mad cow last May 20 in the same province where the Washington state cow may have been born in April 1997.
"Now that two cattle have been discovered who probably ate from the same feed source, there probably are others. Where those cattle are today is anybody's guess," said DeWaal.
Both animals may have fallen ill because they ate feed contaminated with infected remains. US officials are trying to locate 80 head of cattle that entered the United States with the infected cow.
People who eat infected cattle could be at risk of developing variant Creutzfeldt-Jakob disease, a brain-wasting ailment that has killed 130 people, most of them in Britain.
At the OIE, Alex Thiermann said discussion of how to classify the United States was hypothetical until the origin of the infected Holstein was known.
Thiermann, chairman of OIE's standards-setting committee, said by telephone from Paris that officials should focus on reducing the risk of disease because of the large US-Canada cattle trade.
Canada usually ships 1 million head to US buyers each year and is the fourth largest importer of US beef. It has banned imports of US animals older than 30 months.
International trade expert Paul Drazek said ranking the United States as provisionally free of mad cow "is a legitimate question."
"Any other country would be attempting to make the same claim if it could," Drazek said.
Agriculture Undersecretaries J.B. Penn and Bill Hawks leave for Mexico City on Monday to update Mexican officials on the mad cow case. A USDA trade team discussed the beef ban with Japan and South Korea early this week.
Japan, Mexico and South Korea are the leading markets for US beef, accounting for $2.1 billion of exports that total $3.2 billion a year. All three have stopped imports of US beef.