Adult Canadians will soon require passports, or equivalent documents, to enter the United States by land, sea or air.

As of June 1, the Western Hemisphere Travel Initiative will take full effect, meaning most Canadians will need to produce passports, NEXUS cards or enhanced driver's licences, when entering the U.S.

Previously, such documents were only required for U.S. air travel.

Under the new rules, all Canadian travellers aged 16 and up will be required to present a valid passport, or other WHTI-compliant document to enter the U.S.

Canadians aged 15 and under will be able to travel by presenting proof of Canadian citizenship, by using a birth certificate or citizenship card.

Additionally, Canadian citizens aged 18 and under are only required to present proof of Canadian citizenship when traveling with a school or other organized group that is under adult supervision.

The new travel rules also require Mexican, Bermudan and Caribbean travellers to carry the same type of documentation as Canadians when entering the U.S. as of June 1.

Terry Breese, charge d'affaires of the U.S. Mission to Canada, recently posted a note about the WHTI changes to the website for the U.S. embassy in Ottawa.

Breese said that while some Canadians may have concerns about how the new rules will affect their travel plans, the U.S. is working to iron out any anticipated problems.

"No one can forsee every possible issue that might arise at a border which sees about 600,000 people and over US$1.6 billion in goods crossing every single day," Breese wrote in his posting, dated May 22.

"But I can assure you that the United States and its agencies are doing everything we can do to make this transition smooth and painless as the transition was for the air rule."