The Obama administration has zeroed in on Al Qaeda as the driving force behind an attempt to bomb a US-bound airliner on Christmas and promised again to hold accountable those involved in the failed attack.

In his weekly radio and Internet address on Saturday, President Barack Obama said the man suspected of trying to bomb a plane flying to Detroit on December 25 appeared to have been trained by an affiliate of the Islamic militant network.

Obama, who is on vacation in Hawaii, had called for an immediate study of what he termed 'human and systemic failures' that allowed 23-year-old Nigerian Umar Farouk Abdulmutallab to get on a Northwest Airlines flight from Amsterdam to Detroit allegedly with explosives in his clothes.

'The investigation into the Christmas Day incident continues, and we're learning more about the suspect,' Obama said in his address.

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

The president's comments were his most explicit to date tying the suspect with the al Qaeda group.

Michael Leiter, director of the National Counterterrorism Center, said the botched attack proved the group was eyeing new ways to hurt Americans.

'While this attempt ended in failure we know with absolute certainty that Al-Qa'ida and those who support its ideology continue to refine their methods to test our defenses and pursue an attack on the Homeland,' he said in a statement, his first since the incident.

Republicans have accused Obama, a Democrat, of mishandling the incident and not doing enough to prevent attacks on the United States.

Appearing on the defensive, Obama used much of his address to outline his administration's actions to keep the country safe, including withdrawing troops from Iraq, boosting troop levels in Afghanistan and strengthening ties with Yemen, where the suspect spent time before the attack.

Republicans have painted Obama as weak on national security and plan to press the issue ahead of midterm elections in November, when they will challenge the Democrats' control of both houses of the US Congress.

Former Vice President Dick Cheney has led that charge, accusing Obama of pretending the United States was not at war.

Obama, without naming Cheney, responded to that criticism directly, saying he had used the word 'war' in his inaugural address nearly a year ago.

'On that day I also made it very clear 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,' Obama said. 'And make no mistake, that's exactly what we've been doing.'

The president called for an end to the political sniping between Republicans and Democrats on the issue.

'As we go forward, let us remember this -- our adversaries are those who would attack our country, not our fellow Americans, not each other,' he said.

'Instead of succumbing to partisanship and division, let's summon the unity that this moment demands,' he said.

Obama, who repeated his warning that anyone involved in the Christmas Day attack would be held accountable, said the United States had seen successes in helping Yemen fight al Qaeda.

National focus on security lapses some eight years after the Sept 11, 2001, attacks on New York and Washington is competing for attention with Obama's top domestic priorities of job creation and healthcare reform.

Obama has scheduled a meeting with intelligence chiefs on Tuesday at the White House to discuss how to prevent another major security breach.

On Thursday, he received the preliminary findings of the reviews that he ordered.

'I've directed my counterterrorism and homeland security adviser at the White House, John Brennan, to lead these reviews going forward and to present the final results and recommendations to me in the days to come,' Obama said.-Reuters