As many as 1 million U.S. seaport and ship workers must undergo background checks and obtain biometric identification cards as part of a federal program aimed at improving maritime security, according to Reuters. The credentials will supplement, rather than replace, the security cards and clearances workers already must have, sowing doubts about the program among shipping companies and port operators, industry officials said at the Maritime Security Council's annual conference in Fort Lauderdale this week. Enrollment in the U.S. Transportation Worker Identification Credential program, called TWIC, is scheduled to open next week at the Port of Wilmington in Delaware and expand to all U.S. seaports by August 2008.