US tourists traveling to Caribbean countries by air may not have to present their passports when re-entering the US until 31 December 2006. The new passport requirement is part of the Western Hemisphere Initiative section of the Intelligence Reform and Terrorism Prevention Act of 2004 that seeks to strengthen US border security.
The Caribbean tourism sector lobbied intensely in Washington, with the support of the also affected cruise ship industry, against the unfair measure that required passports for Caribbean-bound tourists at an earlier date than Mexico and Canada. Currently, US passport-bearers or green cardholders can travel to the Caribbean countries only presenting a birth certificate and photo ID such as a driver’s license. More than one million US tourists visited the DR in 2004 and an increase is expected this year. Travel sources indicate that only about 20% of Americans have passports.
The Intelligence Reform and Terrorism Prevention Act of 2004 requires that by 1 January 2008 all travelers to and from the Caribbean, Bermuda, Panama, Mexico and Canada to have a passport or other secure, accepted document to enter or re-enter the United States. The US State Department has announced that the timeline for phasing in these requirements is being reviewed and will be published in the Federal Register as soon as it is finalized.
http://www.travel.state.gov/travel/cbpmc/cbpmc_2225.html