The revelation is the latest twist in an increasingly bizarre story about the disruption of an apparent attempt by al-Qaida to strike at a high-profile American target using a sophisticated device hidden in the clothing of an attacker.
The plot, which the White House said on Monday had involved the seizing of an underwear bomb by authorities in the Middle East sometime in the last 10 days, had caused alarm throughout the US.
It has also been linked to a suspected US drone strike in Yemen where two Yemeni members of al-Qaida were killed by a missile attack on their car on Sunday, one of them a senior militant, Fahd Mohammed Ahmed al-Quso.
But the news that the individual at the heart of the bomb plot was in fact an informer for US intelligence is likely to raise just as many questions as it answers.
Citing US and Yemeni officials, Associated Press reported that the unnamed informant was working under cover for the Saudis and the CIA when he was given the bomb, which was of a new non-metallic type aimed at getting past airport security.
The informant then turned the device over to his handlers and has left Yemen, the officials told the news agency. The LA Times, which first broke the news that the plot had been a "sting operation", said that the bomb plan had also provided the intelligence leads that allowed the strike on Quso.
Earlier John Brennan, Barack Obama's top counter-terrorism adviser and a former CIA official, told ABC's Good Morning America that authorities are "confident that neither the device nor the intended user of this device pose a threat to us".
US officials have said the plot was detected in its early stages and that no American airliner was ever at risk.