In response to a new rule requiring most Canadians to carry passports for entry into the U.S., Public Security Minister Anne McLellan said Americans may also have to carry the document to enter Canada.

"Our system has really always worked on the basis of reciprocity," McLellan said outside the House of Commons.

"And therefore we will review our requirements for American citizens and we're going to do that in collaboration with the United States.

"There's no point in either of us going off in a direction without working together to determine how best we can facilitate the flow – a free flow – and movement of low-risk individuals."

McLellan's comments come as the U.S. State Department announced that by 2007, most Canadians will need a passport to enter the United States.

And by 2008, most Americans who visit Canada won't be able to re-enter their country without a passport.

The changes are part of border-security measures the United States will phase in over the next three years that are likely to have a major impact on U.S. tourism and even on the number of Americans who make short trips to Canada.

Canadians without a passport will be barred from entering the United States after Dec. 31, 2006, unless they have a special U.S. "laser visa" border crossing card that includes a fingerprint or other "biometric identifier" such as a retinal scan. Those cards are issued mostly to Mexicans who want to enter the U.S.

Currently, Canadians and Americans are able to enter the United States with little more identification than a driver's licence or a birth certificate, though a passport has sometimes made it simpler to satisfy immigration officers at the border.

The new rules will still allow Canadians to enter the United States without being fingerprinted. The U.S. demands a fingerprint from all other foreign visitors now.

The tighter security will be implemented first between the U.S. and Caribbean countries, then along the U.S.-Mexican border and finally between the U.S. and Canada.

It is likely to start at airports, then spread to land crossings.

The United States is also putting pressure on European countries to speed up introduction of new high-security passports containing a computer chip with a digital photograph.

If the new European Union passports are not in use by the end of October, the United States says it might remove the EU's visa-waiver status. Some analysts have said that could mean a loss of more than $10 billion US to the U.S. travel industry.