The restrictions, in place since Canada's first case of the disease was disclosed in 2003, were eased earlier this year to allow younger cattle to enter the United States.
A prohibition has remained on Canadian animals older than 30 months; levels of infection from mad cow disease are thought to increase with age. Industry officials argue that rules for how cattle are slaughtered would keep the disease from ever entering the human or animal food supply.
The department said it is writing a rule that would lift remaining restrictions on Canadian cattle. Ron DeHaven, administrator of the department's Animal and Plant Health Inspection Service, said the rule will be proposed in six to eight months.
Since discovering its first case in May 2003, Canada has turned up two more cases. The United States discovered two additional cases, one in a cow that was imported from Canada and one in a Texas-born cow. Since the ban was eased, Canada has shipped more than 333,803 cattle into the U.S.