For United States citizens: A valid passport is required for all travel outside of the United States. Passports must not expire within six months after your date of travel in order to be considered valid. For further information and passport requirements, please visit Passports on the U.S. Department of State website.
For Non-United States citizens: You must have a valid passport and any necessary visas for travel. Please carefully verify the existing identification requirements for your particular travel situation with your local consulate. In addition, non-U.S. citizens who have previously been admitted to the United States for permanent residence must carry their Permanent Residence Card (Form I-551), commonly known as a Green Card. Resident aliens not in possession of this must obtain one at the nearest office of the United States Immigration Service.