According to five people familiar with the call, Brennan stressed that the plot was never a threat to the U.S. public or air safety because Washington had “inside control” over it.

Brennan’s comment appears unintentionally to have helped lead to disclosure of the secret at the heart of a joint U.S.-British-Saudi undercover counter-terrorism operation.

A few minutes after Brennan’s teleconference, on ABC’s World News Tonight, Richard Clarke, former chief of counter-terrorism in the Clinton White House and a participant on the Brennan call, said the underwear bomb plot “never came close because they had insider information, insider control.”

A few hours later, Clarke, who is a regular consultant to the network, concluded on ABC’s Nightline that there was a Western spy or double-agent in on the plot: “The U.S. government is saying it never came close because they had insider information, insider control, which implies that they had somebody on the inside who wasn’t going to let it happen.”