U.S. President Barack Obama Saturday for the first time accused an al-Qaeda affiliate of arming and training a young Nigerian man for a thwarted suicide mission to blow up a U.S. airliner.

Obama, in his weekly radio and video address, promised to hold the group, al-Qaeda in the Arabian Peninsula, accountable for the attack. He declared the United States was at war with a "far-reaching network of violence and hatred."

The president's vacation in his home state of Hawaii has been interrupted by the ramifications of the failed attack on a Northwest airlines plane heading to Detroit on Christmas Day.

Obama has reviewed preliminary results of probes ordered into the attack, and said details were becoming clear about the 23-year-old Nigerian suspect Umar Farouk Abdulmutallab.

"We know that he traveled to Yemen, a country grappling with crushing poverty and deadly insurgencies," Obama said in his address, posted on the White House website early Saturday.

"It appears that he joined an affiliate of al-Qaeda, and that this group, al-Qaeda in the Arabian Peninsula, trained and equipped him with those explosives and directed him to attack that plane headed for America."

Previously, U.S. officials have not publicly announced that the Northwest attack was the work of al-Qaeda, although they had noted at a "linkage" with the terror group.

The Arabian Peninsula franchise of al-Qaeda had claimed on Monday the failed Dec. 25 bombing of a jet in a statement picked up by U.S. news agencies.

Abdulmutallab is accused of trying to blow up the plane as it approached Detroit on a flight from Amsterdam, by setting off explosives stitched into his underwear. The attempt failed when he was stopped by passengers.

Obama said that because of past attacks by the al-Qaeda affiliate he had, even before the Christmas Day attempt, stepped up U.S. cooperation with Yemen.

"Training camps have been struck; leaders eliminated; plots disrupted," he said in the address.

"And all those involved in the attempted act of terrorism on Christmas must know – you too will be held accountable."

Obama also put the Northwest attack in the context of the wider threat from terrorism, following complaints from some Republicans that he has not adopted the "war on terrorism" formulation of his predecessor George W. Bush.

He noted that it was almost a year ago since he came to office and delivered his inaugural address.

"On that day I also made it very clear-our, our nation is at war against a far-reaching network of violence and hatred, and that we will do whatever it takes to defeat them and defend our country, as we uphold the values that have always distinguished America among nations."

On Thursday, the US director of national intelligence, Dennis Blair, warned his staff that al-Qaeda attacks were sure to become more "cunning.

In between recreational activities with his family and friends on Friday, Obama consulted top national security advisors to discuss two reviews of the halted attempt to bomb the jet.

He spoke to National Security Council chief of staff Denis McDonough and his top anti-terror advisor John Brennan, a White House official said on condition of anonymity.

Angered by how narrowly tragedy was averted in a country still scarred by the Sept. 11, 2001 attacks, Obama was to spend the weekend deliberating the preliminary reports of two probes he ordered into the Christmas Day attack.

The president plans to meet heads of intelligence agencies and relevant government departments Tuesday in Washington to discuss the findings.

Obama has ordered one assessment of the no-fly list system and a separate investigation into how Abdulmutallab sneaked an explosive device past security at Amsterdam’s Schiphol airport onto a plane bound for the United States.

With the West’s focus on alleged terror havens in Yemen, British Prime Minister Gordon Brown called an international meeting Friday on combating extremism in the country.

Brown's office said the meeting would take place in London on Jan. 28, running "parallel" to  a conference on Afghanistan which is expected to be attended by senior ministers or leaders from about 43 nations.

On Saturday, Yemen welcomed the initiative. "It's a step in the right direction that will mobilize international support for Yemeni development and its efforts to battle unemployment and the effects of poverty," the Saba news agency quoted an official Yemeni spokesman as saying.