If you intend to travel outside the United States – including Canada, Mexico, and the Caribbean – you will need a passport to leave and enter the United States.

As a result of the 9/11 Commission’s recommendations, the Western Hemisphere Travel Initiative (WHTI) requires all travelers to present official documents to establish their identity and nationality. United States citizens, whether travelling as a tourist or business traveler will be required to have a U.S. passport as their form of identification. Children will be required to have their own passports, and will no longer be able to travel without one, even if accompanied by a parent.

The travel document requirements apply to all countries that are not U.S. Territories. If you are travelling directly from the U.S. mainland to a U.S. Territory, you are considered to have not left the United States. However, having a passport can save you a lot of frustration and hassle, in case a border agent requires you to present proof of your identity.

Beginning in June 2009, there will be no exceptions allowed. Mexico and Canada will require a passport or a passport card as proof. No matter if you leave the United States by air, car, boat, or by foot – you will need passport documentation. Cruise ship travelers are subject to the same strict requirements.

So if you’re planning a trip that takes you anywhere outside the U.S. mainland border, avoid problems and disappointment. The only sensible and prudent thing to do is to travel with your passport.