U.S. and Yemeni officials say the supposed would-be bomber at the heart of an al-Qaeda airliner plot was actually an informant working for the CIA.

Last month, U.S. intelligence learned that al-Qaeda's Yemen branch hoped to launch a spectacular attack using a new, nearly undetectable bomb aboard an airliner bound for America, officials say.

But the man the terrorists were counting on to carry out the attack was actually working for the CIA and Saudi intelligence, U.S. and Yemeni officials told The Associated Press on Tuesday.

The dramatic sting operation thwarted the attack before it had a chance to succeed.

It was the latest misfire for al-Qaeda, which has repeatedly come close to detonating a bomb aboard an airliner. For the United States, it was a victory that delivered the bomb intact to U.S. intelligence.

The officials spoke to the AP on condition of anonymity because of the sensitivity of the operation. The co-operation of the would-be bomber was first reported Tuesday evening by the Los Angeles Times.

FBI analyzing explosive

The FBI is still analyzing the explosive, which was intended to be concealed in a passenger's underwear. Officials said it was an upgrade over the bomb that failed to detonate on board an airplane over Detroit on Christmas 2009. This new bomb contained no metal and used a chemical — lead azide — that was to be a detonator in a nearly successful 2010 plot to attack cargo planes, officials said.

Security procedures at U.S. airports remained unchanged Tuesday, a reflection of both the U.S. confidence in its security systems and a recognition that the government can't realistically expect travellers to endure much more. Increased costs and delays to airlines and shipping companies could have a global economic impact, too.

"I would not expect any real changes for the travelling public," said House intelligence committee chairman Mike Rogers. "There is a concern that overseas security doesn't match ours. That's an ongoing challenge."