Washington:
White House officials on Sunday denounced Osama bin Laden and gave no indication that a new audio message purportedly by the al-Qaida leader had triggered heightened alarm about renewed attacks.
In a short recording carried by the Al-Jazeera Arabic news channel, a man - purportedly bin Laden - addressed US President Barack Obama, saying the Detroit attack was intended as a message similar to that of September 11, 2001. The voice also warned that more attacks against the US would be forthcoming.
White House spokesman Robert Gibbs said "nobody has had a chance to authenticate that tape," but declined to comment on whether the US believes bin Laden played any role in the Christmas incident.
Speaking on "Fox News Sunday," Gibbs said, "everybody in this world understands that this is somebody that has to pop up in our lives over an audio tape because he's nothing but a cowardly, murderous thug and terrorist that will someday, hopefully soon, be brought to justice."
On Christmas Day, Nigerian national Umar Farouk Abdulmutallab attempted to blow up the Northwest Airlines flight he was sitting on as it approached Detroit Metro Airport. But the bomb he was hiding in his underwear failed to explode.
He told federal agents shortly afterwards that he had been trained and instructed in the plot by al-Qaida operatives in Yemen.
Al-Qaida in the Arabian Peninsula originally took credit for the attack and Sunday's message is viewed by many as an attempt by bin Laden to show he remains in direct command of al-Qaida's many offshoots around the world.
Analysts had previously suggested that al-Qaida's offshoots in North Africa, the Arabian Peninsula and elsewhere were operated independently from bin Laden, who is believed to be somewhere in the Afghanistan-Pakistan border region.
There was no way to confirm the voice was actually that of bin Laden, but it resembled previous recordings attributed to him.
In the past year, bin Laden's messages have concentrated heavily on the plight of the Palestinians in attempt to rally waning support across the region.
Many analysts believe that bin Laden is worried about Obama's popularity across the Middle East, so the al-Qaida leader has shifted focus onto the close US-Israeli relationship.