Officials say a double-agent who fooled al-Qaida's terror group in Yemen possessed a British passport that was provided by that country's intelligence agency, MI-6, as part of the ruse.
The would-be suicide bomber's British citizenship would have made him an attractive terror recruit, because he could travel more freely to western countries.
Instead, he sneaked al-Qaida's underwear bomb out of Yemen, delivering it to the CIA in a major intelligence coup.
The two officials talked on condition of anonymity because they were not authorized to speak publicly about the plot.
The operation shows the close cooperation among the U.S., Britain, and Saudi Arabia, whose intelligence service played a major role in infiltrating the organization, and helping communicate with the agent.
The British intelligence role was first reported by NBC News.