US President Barack Obama has said it appeared the man suspected of trying to bomb a Detroit-bound plane on Christmas Day was a member of al-Qaeda and had been trained and equipped by the Islamic militant network.

Defending his administration's counterterrorism efforts amid scathing Republican criticism, Obama said he received preliminary results of the reviews he ordered into air travel screening procedures and a "terrorist watchlist system" and expected final results in the days to come.

Obama, who is on holiday 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 on 25 December 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 weekly radio and internet address, posted on the White House website on Friday local time.

"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.

Republicans have accused Obama of mishandling the incident and not doing enough to prevent attacks on the US.

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."

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.

"I've made it a priority to strengthen our partnership with the Yemeni government – training and equipping their security forces, sharing intelligence and working with them to strike al-Qaeda terrorists," he said.

"And even before Christmas Day, we had seen the results. Training camps have been struck; leaders eliminated; plots disrupted."

US intelligence and counterterrorism officials, speaking last week on condition of anonymity, said spy agencies picked up important information about Abdulmutallab, and about the intentions of al-Qaeda leaders in Yemen, in the months before the attempted bombing.

National focus on security lapses some eight years after the 9/11 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.