The United States and the European Union signed an agreement yesterday to share airline passenger records as a way to search for wanted criminals or suspected terrorists on transatlantic flights.

In a ceremony at the Ronald Reagan Building, Homeland Security Secretary Tom Ridge said the long-negotiated agreement represented "an essential security measure that allows us to link information about terrorists and serious criminals" while providing privacy protections for airline passengers.

U.S. and European airlines and reservation companies will exchange passenger information with customs officials up to three days before a flight's departure, officials said.

Gunter Burghardt, the EU ambassador to the United States, said the agreement was "further concrete evidence that the U.S. and EU share a common goal of fighting terror," despite differences in law. "Today we are at the end of the beginning . . . of a wider effort," he said.

Some EU politicians who view the deal as a violation of Europe's strong privacy laws could still challenge the agreement in the European Court of Justice. "We believe the agreement would withstand a legal challenge," said C. Stewart Verdery Jr., the assistant homeland security secretary for policy.

The Homeland Security Department plans to begin negotiations with other countries that are interested in forming a legal agreement to exchange information about their passengers, Verdery said. He would not identify those countries.

Passengers' names, addresses, phone numbers, credit card information, seat location and, in some cases, hotels will be transferred to the destination country before departure. U.S. officials agreed to block certain fields such as meal preference and health considerations because European officials argued those items were private.

The information will be kept for 31/2 years and will be used as part of a controversial computer screening program under development by the Transportation Security Administration, known as CAPPS 2. It aims to add an additional layer of security to air travel by using databases of commercial information to verify each passenger's identity. Every passenger on U.S. and overseas flights will be assigned a risk score.

As part of the agreement signed yesterday, EU representatives agreed to allow U.S. officials to use passenger records to test the CAPPS 2 program, but only after U.S. airlines agree to do the same.

Airlines that operate in the United States and Europe expressed relief yesterday that they would no longer find themselves between two opposing legal systems. "We certainly see this as a positive step forward," said Wanda Warner, spokeswoman for the International Air Transport Association.

EU Ambassador Gunter Burghardt, far left, signs an agreement Friday to share passenger data with the United States as Tom Ridge, right, receives another from EU transportation official Lars-Olaf Hollner. Irish Ambassador Noel Fahey, center, looks on. The man standing by Burghardt was not identified.