Passport-photo vendors have been given updated specifications for taking the pictures, to help provide proper illumination and other specifications to maximize the effectiveness of the face-recognition methods, Moss said. The department hopes the program will pay for itself through a surcharge of about $10 per passport.
Rebecca Dornbusch, deputy director of the International Biometric Industry Association, said that the U.S. view has long been that fingerprint technology is preferred but that it was important to be in harmony with the international standard.
"The important thing to recognize is that it is an improvement," Dornbusch said of the face-recognition requirement. But she said her organization is encouraging the State Department to "continue to implement as many biometrics as they can, so they can ensure . . . the most secure protection."
But James L. Wayman, director of biometric identification research at San Jose State University in California, said face recognition is not reliable enough to be useful.
"Facial recognition isn't going to do it for us at large scale," Wayman said. "If there's a 10 percent error rate with 300 people on a 747, that's a problem."
According to tests by the National Institute for Standards and Technology, two fingerprints provide an accuracy rate of 99.6 percent. With face recognition, if the pictures are taken under controlled circumstances with proper illumination, angles and facial expression, the accuracy rate was 90 percent.
"The numbers would be better today, but they are not going to be comparable with fingerprints," Wilson said. Even a person's aging can affect results, especially with children.
Dennis Murphy, a spokesman for the Department of Homeland Security, which employs passport-control agents, said the agency has not yet determined how images of travelers will be taken to compare against the photos on the embedded chips.
He said the department will put out its own request for bids for equipment -- probably something similar to a Web camera -- that visitors would look into for a photograph. The bid documents, he said, will specify standards for making the face-recognition match as accurate as possible.
Murphy declined to comment on the State Department's decision not to include fingerprint data in the passports.
Some said the government feared a potential backlash.
"The simple answer is that they don't want to put in a fingerprint biometric because they don't want to deal with the political recriminations" said Robert D. Atkinson, a member of a national security task force at the nonprofit Markle Foundation, which studies digital issues. Atkinson also heads the Progressive Policy Institute, a part of the Democratic Leadership Council.
Privacy advocates argue that taking fingerprints is no more invasive than face recognition, and certainly not more than other Bush administration initiatives launched since Sept. 11, 2001, that have sought to link databases of buying habits, bank accounts and other personal information to try to predict terrorist activity.
The fingerprint data could be placed on the passport chip but not saved in a database, they said, removing the concern over a central government repository. The data on the chip is simply matched against a finger scan when the traveler arrives at the passport control station.
"My passport belongs to me," said Ian "Gus" Hosein, a senior fellow at Privacy International, a Britain-based advocacy group. "They should not be using this as a back door to international databases."