WASHINGTON (AP) — Senior U.S. officials offered a more nuanced picture Thursday of the threat they believe is posed by an al-Qaida cell in Syria targeted in military strikes this week, even as they defended the decision to attack the militants.

James Comey, the FBI director, and Rear Adm. John Kirby, the Pentagon spokesman, each acknowledged that the U.S. did not have precise intelligence about where or when the cell, known as the Khorasan Group, would attempt to strike a Western target.