Canada's immigration minister says increased co-operation with the United States on immigration policy is unlikely to lead to identical immigration laws.

Elinor Caplan responded to calls by U.S. Ambassador Paul Cellucci for the United States and Canada to establish a North American perimeter. Cellucci said that would allow immigration officials from both countries to work together.

"The best way to do it is to have this perimeter concept," he said. "It doesn't mean we have to be exactly the same, but I think the more common the immigration and refugee laws are the easier it is to have this perimeter which will protect both countries."

A possible Canadian connection to last week's attacks in New York and Washington hasn't been determined, but security agencies in Canada say terrorist groups are operating in the country.

After four jets were hijacked and used as missiles to attack the World Trade Center and the Pentagon, long-standing questions about Canada's immigration and refugee policies were given new life.

The Opposition has been reiterating its demands for tougher laws to control who gets into the country.

The Liberal government has new immigration laws before the Senate. Caplan says changes may have to be made to those bills but she says a common policy with the U.S. is unlikely.

"I understand what the ambassador is saying, and I agree that we need to work as closely together as possible," she said. "We're separate countries, so it's unlikely that we'll ever have identical laws."

Caplan says officials from both countries need to work together to share information about potential terrorists.

She and Cellucci agree an open border is key to maintaining the more than $1 billion in trade that passes between the two countries every day.