Despite cost increases caused by the deterioration of U.S. dollar exchange rates, Canada rightfully remains a popular destination for Americans.

But in three months, getting across the border is expected to become more difficult and time-consuming, when stricter federal rules requiring proper identification for land crossings are scheduled to take effect.

Long lines already are forming along the Mexican border as U.S. border agents start limited enforcement of these rules imposed by the Western Hemisphere Travel Initiative, the government's post-9/11 attempt to gain control of national borders.

Until recently, oral declarations have been sufficient proof of U.S. residency to cross the Canadian and Mexican borders by car or on foot.

Unless the date is changed, beginning Feb. 1, everyone, including children, will be required to have either a passport or WHTI compliant documentation. That includes both a government-issued photo ID (such as a driver's license) as well as proof of citizenship, such as a birth certificate, naturalization certificate, visa or green card.

The first phase of the WHTI crackdown began in January, when all travelers arriving by air from Canada, Mexico, Bermuda and most Caribbean countries were required to provide a passport at U.S. immigration, exactly as if they were coming from anywhere else.

The tsunami of passport applications resulting from this edict flooded State Department offices, creating long delays and headlines and complicating the lives of thousands of travelers. The rule was temporarily relaxed, but that period has elapsed.

But these airport border disruptions are nothing compared to the chaos many experts expect at every U.S. land crossing with Mexico or Canada, from San Diego to West Quoddy Head, Maine, when the other WHTI shoe drops.

Eventually, perhaps as soon as 2009, passports will be required of all travelers.

Then, the sole exceptions to the passport requirement will be NEXUS and SENTRI passholders. Both "trusted traveler" programs were established jointly by U.S. and Canadian customs in 2002 to expedite border crossings, especially for those who do it frequently.

The passes can provide faster clearance at 11 U.S./Canada border crossings and seven Canadian airports.

Citizens and permanent residents of either country can apply for the pass (866-639-8726 or www.cbp.gov), which costs $50 and involves an interview and a background check, complete with documentation, fingerprints, photographs and digital iris photographs. Successful applicants are issued a card that must be renewed every five years.

Although NEXUS cardholders get screened more quickly, they're still subject to all the standard border checks and procedures. Major crossings have special NEXUS lanes, but to use the lane, everyone in the vehicle, including children, must have a valid card. So they're not a solution, except for frequent travelers.