The U.S. government on Friday said that effective January 8, 2007, citizens of the United States, Canada and Mexico must present a passport or one of two other approved documents to enter the United States by air or sea from the Western Hemisphere.

The plan, which must undergo public comment before going into effect, moves the deadline back a week from its original date of January 1 to accommodate holiday travel, the Department of Homeland Security said in a statement.

Under the rule, which implements part of a 2004 law and also covers Bermudans, the government will accept a Merchant Mariner Document — issued by the U.S. Coast Guard to merchant mariners — instead of a passport.

Some Canadian and U.S. citizens enrolled in a pilot program called NEXUS Air can also enter the country by presenting the identity card they have been issued that includes a computer chip with a photograph of their iris.

Previously, U.S. and Canadian citizens were allowed to enter the United States from the Western Hemisphere if they presented an identification document like a driver’s license. Some Mexicans could also enter without a passport if they had a special border crossing card.

A second stage of the program will be implemented by January 1, 2008. It will require similar documents for citizens of the United States and Canadians, Mexicans and Bermudans arriving from the Western Hemisphere through U.S. land borders.

The program is separate from another effort to photograph and fingerprint visitors from most foreign countries when they enter the United States.