While the Bush administration had defended its program of wiretapping without warrants as a vital tool that saved lives, a new government review released Friday said the program’s effectiveness in fighting terrorism was unclear.

The report, mandated by Congress last year and produced by the inspectors general of five federal agencies, found that other intelligence tools used in assessing security threats posed by terrorists provided more timely and detailed information.

Most intelligence officials interviewed “had difficulty citing specific instances” when the National Security Agency’s wiretapping program contributed to successes against terrorists, the report said.

While the program obtained information that “had value in some counterterrorism investigations, it generally played a limited role in the F.B.I.’s overall counterterrorism efforts,” the report concluded. The Central Intelligence Agency and other intelligence branches also viewed the program, which allowed eavesdropping without warrants on the international communications of Americans, as a useful tool but could not link it directly to counterterrorism successes, presumably arrests or thwarted plots.

So much for that talking point that all that spying kept us safe from another terrorist attack.