The Bush administration is asking Congress to give countries more time to produce high-tech passports for their citizens who want to travel to the United States.

In a joint letter to the chairman of the House Judiciary Committee, the secretaries of state and homeland security ask that foreign governments be given two more years to comply with the new U.S. requirements for passports.

Secretary of State Colin Powell and Homeland Security Secretary Tom Ridge said none of the 27 countries whose citizens are affected can meet the October 26 deadline for machine-readable passports, known as "biometric" passports. They suggest setting a new deadline of December 2006.

If the deadline is not extended, countries whose citizens do not normally need a visa to enter the United States will be obliged to get one. Mr. Ridge and Mr. Powell warned of "grave consequences" if that happens.

Under laws passed in 2001 and 2002, countries whose citizens can enter the United States without first obtaining a visa must have a biometric passport. Most of the affected countries are in Europe, although the group also includes Japan, Australia, Brunei, and New Zealand.

Asked about the letter, officials said they are not yet prepared to publicly comment on the matter. But Rebecca Dornbusch of the International Biometric Industry Association - a trade group of the electronic identification industry - says no government could meet the congressionally mandated deadline.

"It was an unrealistic deadline to expect countries to put full systems in place and change the way they've been processing their applications for passports for years," she said.

Biometrics is, in essence, automated identification by computer. The document, be it a passport or I.D. card - has a computer chip embedded within containing facial features and other data. A machine scans the document to ensure that the data in the chip matches the bearer of the document.

"What it would do is a biometric match," explains Ms. Dornbusch. "So it would be saying, the person who is holding this document - a passport - is the person standing before me. By using technology that matches the template on the card, on the passport, to the person standing in front of them, they're able to verify an identity and the person can enter into the system, or enter into the country."

Britain, Germany, and Japan are expected to begin issuing biometric passports in 2006. In his letter, Secretary Powell said the transition to U.S. biometric passports is expected to begin later this year and be completed by 2005.

Biometric technology is growing. It is already used by some governments for security badges or national identification cards. The International Civil Aviation Organization has already established its own biometric standards. Some U.S. states are examining its possibilities for drivers' licenses, and the state of Connecticut began using it in 1996 to prevent fraud among welfare recipients. But the issue is sensitive among civil liberties groups who fear that a great deal of personal data will be stored on an embedded document's computer chip.