DUBAI (Reuters) - Al Qaeda leader Osama bin Laden claimed responsibility for the failed December 25 bombing of a U.S.-bound plane in an audio tape aired on Sunday, and vowed to continue attacks on the United States.
In his message addressed "from Osama to (U.S. President Barack) Obama," bin Laden said the attempt to blow up the jet as it neared Detroit was a continuation of al Qaeda policy since the September 11, 2001 attacks on the United States.
White House adviser David Axelrod said he could not confirm the authenticity of the tape, which was broadcast by Al Jazeera television before international meetings this week on how to deal with militancy in Afghanistan and Yemen.
But Abdelbari Atwan, editor of Al-Quds-Al-Arabi newspaper who met the al Qaeda leader in 1996, said: "It is bin Laden's voice and style. The poetry, the references he makes are identifiably his."
Bin Laden praised the Nigerian who has been charged with trying to blow up Northwest Flight 253.
"The message sent to you with the attempt by the hero Nigerian Umar Farouk Abdulmutallab is a confirmation of our previous message conveyed by the heroes of September 11," he said. "If it was possible to carry our messages to you by words, we wouldn't have carried them to you by planes."
The botched attack by the Yemen-based regional wing of al Qaeda on Christmas Day, and subsequent threats in Yemen, raised global pressure for a crackdown, helping to prompt Sanaa to declare an open war on the militant group within its territory.
Defense and counterterrorism officials say Washington quietly has been supplying military equipment, intelligence and training to Yemen to destroy suspected al Qaeda hide-outs.
Since the attempted bombing, Yemen has launched a series of air strikes targeting al Qaeda leaders and has declared that some top regional leaders, including Qasim al-Raymi and Ayed al-Shabwani, have been killed.
But Al Qaeda denies the claims. Yemen subsequently attacked the rural home of Shabwani but gave no hint on the result.
On Sunday's tape, bin Laden cited Washington's support for Israel as a motivator for more attacks on the United States, and vowed to keep on as long as Palestinians cannot live in peace.
"Our attacks against you will continue as long as U.S. support for Israel continues," bin Laden said. "It is not fair that Americans should live in peace as long as our brothers in Gaza live in the worst conditions."
White House adviser Axelrod attacked bin Laden on CNN TV. "Assuming that it is him, his message contains the same hollow justifications for the mass slaughter of innocents that we've heard before," he said.
Libyan analyst and former bin Laden associate Noman Benotman said the tape was intended to send a message to the Arab world.
"It's a very smart 'back to basics' message, reminding his audience it is all about Israel and America. His main audience is the Arab World, where al Qaeda has lost substantial moral support," Benotman said.
"The reference to September 11 gives al Qaeda's actions a continuity and a definable shape."
Britain, before the meetings on Afghanistan and Yemen Wednesday and Thursday in London, raised its terrorism threat level to "severe" -- the second highest level -- on Friday.
The decision to raise the level from "substantial" means security services now consider an attack in Britain, a key U.S. ally, to be highly likely. But the government said it had no information to suggest an attack was imminent.
Yemen gained a reputation as an al Qaeda haven after the 2001 attacks. It came again under a spotlight after crackdowns on the group in Pakistan and Afghanistan raised fears Yemen was becoming a training and recruiting center for militants.
The high profile London meetings on Afghanistan and Yemen are aimed at stabilising both nations and stopping al Qaeda from using either country as a base.
The Afghanistan meeting on Thursday is meant to chart a path for the country to take greater responsibility for its security. Britain says the conference also will look at how Afghanistan's neighbors could work together to help stabilize it.
On Wednesday, foreign ministers of Yemen's main Western and Gulf partners will also meet to try to mobilize support for the country and identify what needs to be done by the government and its allies to tackle its challenges.
In addition to fighting a resurgent al Qaeda, Yemen also is fighting a separate northern Shi'ite rebellion and trying to contain southern separatists.
Additional reporting by Amena Bakr in Dubai and Mohamed Sudam in Sanaa; Writing by Cynthia Johnston; Editing by Michael Roddy