"The device was for use by a suicide bomber on an airliner," the official told AFP on condition of anonymity.
The plot by al Qaeda in the Arabian Peninsula (AQAP) was uncovered at an early stage and represented a "success story" for US authorities working closely with allies, the official said.
"At no point were any airlines at risk," the official added.
The bomb was similar in scale to one employed in a failed attempt to blow up a US-bound airliner on Christmas Day in 2009 but there were "notable differences," the official said.
"This suggests AQAP is adapting its methodology, its tactics et cetera."
The White House, too, confirmed that the plot never posed any risk to the public.
President Barack Obama "was assured that the device did not pose a threat to the public," National Security Council deputy spokeswoman Caitlin Hayden said in a statement, adding that the president had directed agencies "to take whatever steps necessary to guard against this type of attack."
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Hahahhahaa. Same very old trick played again by USA. CIA need to come up with fresh dramas. This soap is extremely old now.
Job well done by CIA. these terrorists should not be given any room.