OTTAWA -- The U.S. ambassador in Ottawa is urging an expansion of the North American Aerospace Defence Command and increased co-operation between intelligence forces, saying his country is vulnerable to terrorist attacks launched from inside Canada.

The threat of terrorism has not receded since Sept. 11, 2001, Paul Cellucci told a group of about 40 francophone business people during a luncheon meeting yesterday.

"The threat is real and we need to continue to work together to make sure that the terrorists do not strike again," he said. "Our shared geography alone makes it inevitable that the terrorists would consider using Canada as a potential launching pad into the United States."

Mr. Cellucci, whose political appointment to Ottawa is expected to end within months, used his speech to talk about the relationship between the two countries and touched on the sensitive issue of mad-cow disease (bovine spongiform encephalopathy) that has prevented Canadian cattle from being sold in the United States.

The ambassador -- a former Republican governor -- said President George W. Bush and his administration wanted the beef ban lifted but people within the Democratic Party, including Tom Daschle, the Senate Democratic Leader from South Dakota, have prevented such action.

While he went on to talk about energy and environmental issues, the hardest-hitting portion of Mr. Cellucci's speech was security. His country, he said, cannot defend itself without Canada's help.

"Working together with the Royal Canadian Mounted Police and CSIS [Canadian Security Intelligence Service] and other law-enforcement and intelligence agencies here in Canada is quite critical to the protection of the people in the United States," the ambassador said, "and also to the protection of the people of Canada."

NORAD, a joint military command between Canada and the United States that was established in 1958 to patrol the skies and warn of potential attacks by aircraft, missiles or space vehicles, works well, he said.

He went on to say that the controversial missile-defence system proposed by his country could be "an important piece" of NORAD expansion and urged Canada to sign on.

NDP Leader Jack Layton, who has made opposition to missile defence one of the key planks for his party during this session of Parliament, said he found Mr. Cellucci's statements disturbing.

"Our view is that embarking on missile defence accelerates the arms race and reduces the security of people, not only in Canada, but all around the world," Mr. Layton said, "and the notion that Canada could be labelled as a potential launching pad for terrorism is certainly very worrisome."