WASHINGTON (AP) -- Senators from Western ranching states are objecting to a Department of Agriculture plan they say would loosen restrictions on beef and lamb imports from Argentina.

Argentina has seen outbreaks of foot-and-mouth disease, a highly contagious viral disease that affects cloven-hoofed animals like cattle and pigs. The senators asked the department to analyze the cost of the proposal -- including the cost of a foot-and-mouth disease outbreak -- before implementing the policy. Questions remain about the effectiveness of animal disease controls and tracking in Argentina, the senators said.

A bipartisan group of senators from Montana, Wyoming, North Dakota, South Dakota, New Mexico and Missouri signed the letter.