For a Cruise: A passport is not required if you are traveling in and out of a U.S. port at this time, but you are encouraged to travel with a valid one. You may sail with an official birth certificate and a supporting government-issued photo ID, like a driver's license or identity card. If your birth certificate does not match your government-issued photo ID, then you must include other supporting documentation to confirm your name, such as a marriage license.
For all other international travel, a valid passport is required. Passports must be valid for at least 6 months after the end date of your travel.