LOS ANGELES --- As of June 1, the U.S. Department of Homeland Security is enforcing rules requiring U.S. citizens to carry passports or passport cards when traveling by car or cruise ship to Mexico, Canada and the Caribbean.

U.S. citizens were already required to carry passports on all plane trips outside the U.S., but on June 1 that requirement extended to cruise and car trips as well. 

However, those traveling by cruise or car outside the U.S. will also have the less expensive option of using a "passport card" rather than a full passport. A passport card is about the size of a driver's license and can be a more convenient way to quickly present identification.

"The passport cards are a budget-friendly option because they cost $45 while a first-time passport costs $100," said Kim Wilde, manager of Auto Club travel product management. "However, since the passport card may only be used for cruise or drive trips outside the U.S., a full passport may be a better option for many people."

An International Driving Permit (IDP) is recommended and may be required for those planning to drive in foreign countries where English is not the official language. The IDP serves as a translation of the traveler's driver's license and must be carried along with the traveler's valid U.S. driver's license and passport.

International Driving Permits are available for $15 through AAA and the American Automobile Touring Alliance, which are the only organizations authorized by the U.S. government to issue IDPs.

The new rules were recommended by the 9-11 Commission years ago. The change in policy is the final implementation of the Western Hemisphere Travel Initiative.