OTTAWA – Security concerns since Sept. 11 are changing the rules, even when it comes to old friend Canada and the world’s longest undefended border.

There are no plans to post military troops along the 4,000-mile boundary from Alaska to Maine, but U.S. Ambassador Paul Cellucci made clear in an interview Wednesday that Canada won’t be exempt from new security rules.

“As we go along, security will be paramount, there’s no doubt about it,” said Cellucci, a former Massachusetts governor who was appointed ambassador a few months before the Sept. 11 attacks. “But we also, to the extent that problems are created, want to solve the problems.”

A new U.S. system for keeping track of foreign visitors has angered Canada for targeting people born in countries linked to terrorism, no matter their citizenship.

The system authorizes officials to fingerprint and photograph travelers who were born or hold citizenship in five countries that the United States says sponsor terrorism: Iran, Iraq, Libya, Sudan and Syria.

Canada warned its citizens born in those countries to avoid travel to the United States and protested to Washington after a Syrian-born Canadian was detained during a transit stop in New York and deported to Syria.

With the U.S. Congress requiring expansion of the entry-exit system to all foreign visitors by the end of 2005, Canadians used to cruising past border posts with the wave of a passport could face far greater scrutiny.

Deputy Prime Minister John Manley questioned the plan after a Dec. 6 meeting in Washington with Tom Ridge, secretary-designate for homeland security. Manley acknowledged the U.S. security concerns, but wondered how the system could be implemented without choking bilateral trade worth more than $1 billion a day.

Air travelers to either country already fill out entry forms. Cellucci said the problem is road traffic, which moves largely without paperwork. But requiring tens of thousands of motorists a day to fill out forms could cause massive gridlock.

Ridge and Manley are considering high-tech solutions, with suggestions including a national identity card that could be read by scanners.

“Is it feasible to do it in a way that doesn’t impede the flow of legitimate commerce and traffic? I think that’s the first question,” Cellucci said.

“If the answer is ‘Well, the technology hasn’t been developed yet,’ then I think it’s something that we’ll have to talk to congressional leaders about,” he added.

Canada and the United States agreed last year to a 30-point plan to enhance border security while maintaining the flow of people and goods. It includes creating “fast lanes” for pre-cleared trucks and people, increased sharing of intelligence, more coordinated immigration policies and joint border enforcement teams.

Canada also has followed many U.S. security policies since Sept. 11 – banning and seizing the assets of terrorist groups, toughening security laws, and increasing security at airports and other entry points.

The entry-exit system, however, is a unilateral U.S. move. Border gridlock would hurt both economies, but Canada – which sends 85 percent of its exports to the United States, compared to 20 percent of U.S. exports going to Canada – is more vulnerable.

Cellucci denied the system signaled a lack of confidence by the U.S. government in Canada’s anti-terrorism effort or reflected any problems in the U.S.-Canada relationship.

Recent incidents have prompted speculation of a growing rift between the neighbors – a top aide to Prime Minister Jean Chretien was overheard calling President Bush “a moron” – but Cellucci dismissed any problems as minor irritants.

“Canada’s been at our side in Afghanistan, here in North America cracking down on terrorists, they were on our side pushing to get that new resolution at the United Nations on Iraq,” he said. “We’re grateful to have such good neighbors.”