Former U.S. Supreme Court Justice Sandra Day O’Connor said Monday she believed the war on terror was only at the beginning, and the challenge of balancing national security against the protection of civil liberties will be a key issue in the coming years.

O’Connor, speaking in the tiny mountainous principality of Liechtenstein, said the United States had at times failed to strike that “delicate balance” correctly in the past, erring too greatly on the side of national security.