The date was disclosed Tuesday by Homeland Security Secretary Michael Chertoff in an interview with The Associated Press. The Homeland Security Department plans to announce the change on Wednesday.
Until now, the department had not set a specific date for instituting the passport requirement for air travelers, though the start had been expected to be around the beginning of the year. Setting the date on Jan. 23 pushes the start past the holiday season.
The requirement marks a change for Americans, Canadians, Bermudians and some Mexicans.
Currently, U.S. citizens returning from other countries in the hemisphere are not required to present passports but must show other proof of citizenship such as driver's licenses or birth certificates.
Visitors from most countries in the hemisphere are required to show passports. However, people from Canada, Bermuda — and those from Mexico who enter the U.S. frequently and have special border-crossing cards — have been allowed to use other forms of identification, including driver's licenses.
"Right now, there are 8,000 different state and local entities in the U.S. issuing birth certificates and driver's licenses," Chertoff said. Having to distinguish phony from real in so many different documents "puts an enormous burden on our Customs and Border inspectors," he said.
In a few cases, other documents still may be used for air entry into the U.S. by some frequent travelers between the U.S. and Canada, members of the American military on official business and some U.S. merchant mariners.
Under a separate program, Homeland Security plans to require all travelers, including Americans, entering the U.S. by land or sea to show a passport or an alternative security identification card starting as early as January 2008.
The Homeland Security Department estimates that about one in four Americans has a passport. Some people have balked at the $97 price tag.
The Sept. 11 Commission said in its report, "For terrorists, travel documents are as important as weapons."
The commission recommended strengthening security of travel documents. A 2004 law passed by Congress mandated the change to require passports as the only acceptable travel document, with few exceptions, but the exact date had been in question.
Canadian officials and some members of Congress from border states have expressed concern that the changes could interfere with travel and commerce.
Chertoff said his agency's data revealed that in September 2006, 90 percent of passengers leaving from Canadian airports had passports. The department estimated that 69 percent of U.S. travelers to Canada, 58 percent of U.S. travelers to Mexico, and 75 percent of U.S. travelers to the Caribbean hold passports.
"Could James Bond and Q come up with a fake passport" that could fool inspectors? Chertoff asked, referring to the fictional British spy and his espionage agency's technical genius. Of course, he replied, "Nothing is completely perfect."
Still, he said that with new technology, it is increasingly difficult to forge passports, and having just one document to scrutinize should make inspection easier for both inspectors and travelers.
By BEVERLEY LUMPKIN