The Obama administration is launching a pilot program to collect biometric information from non-U.S. citizens when they leave the country. The federal government began testing the system at two big city airports this week. The initiative is the latest effort, following the 2001 attacks on the World Trade Center and the Pentagon, to keep track of those who come to and depart from the United States.

Fingerprints and other physical identifiers, called biometrics, are seen as a fail-safe way to verify identity and defeat imposters. Since 2004, the United States has collected biometric information from foreign visitors upon arrival, but not departure. That is now changing.

Robert Mocny, who leads the US-VISIT program, said "We want to have biometric exit procedures because we want to have a better sense of who is in the country and who has left the country."

The new system is being tested at airports in Atlanta and Detroit. Departing non-citizens are required give fingerprints that will be compared with prints taken when they applied for their U.S. visas or resident alien cards. The federal government aims to extend the program to all U.S. airports and seaports next year.

The 9/11 Commission that investigated the 2001 terrorist attacks on the U.S. recommended the government maintain accurate lists of those who enter and exit the country.

"Once a visa is issued and tied with a biometric, once a passport is issued and tied to a biometric, that passport or visa cannot be used by anybody else," added Mr. Mocny.  "There are tens of millions of lost or stolen passports that circulate the globe on the black market used by international criminals and terrorists. This [biometric verification] puts a stop to that."

Mocny says the United States intends to extend biometric identity verification to exit points along the U.S. borders with Canada and Mexico. Just when that will occur is not clear, as U.S. officials admit significant logistical challenges must be overcome to allow such screening of vehicular traffic.