But the president until now had avoided citing that until analysts were further along in their assessment of the group’s activities and its ties to Umar Farouk Abdulmutallab, the 23-year-old Nigerian charged with trying to blow up the airliner.

Image President Obama shared ice shavings on Friday with his daughter Malia in Hawaii, where he taped his Saturday address. Credit... Alex Brandon/Associated Press

“We’re learning more about the suspect,” Mr. Obama said. “We know that he traveled to Yemen, a country grappling with crushing poverty and deadly insurgencies. 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.”

Mr. Obama’s comments indicated that he and the government largely accepted the accounts offered by Mr. Abdulmutallab since he was taken into custody and by Al Qaeda in the Arabian Peninsula in a statement on the Web. The National Security Agency had intercepted communications among Qaeda leaders months ago talking about an unnamed Nigerian preparing to attack, but the government never correlated that with information about Mr. Abdulmutallab’s radicalization collected by embassy officials in Nigeria from the suspect’s father.

On Saturday, the director of the National Counterterrorism Center, Michael E. Leiter, made his first public comments on the bombing attempt. The center has come under sharp criticism for not connecting various warnings before the attempt.

“The failed attempt to destroy Northwest Flight 253 is the starkest of reminders of the insidious terrorist threats we face,” Mr. Leiter said in a statement. “While this attempt ended in failure, we know with absolute certainty that Al Qaeda and those who support its ideology continue to refine their methods to test our defenses and pursue an attack on the homeland.”

Some changes have been made in the past week, and others are being forwarded to Mr. Obama for consideration. The terrorism center has elevated several hundred individuals from a handful of countries, including Yemen and Nigeria, to be put on watch lists rather than merely being entered in a terrorism database.

Some of these individuals, as well as others who were already on the terrorism watch list, have now been placed on more selective lists that subject them to secondary screening before boarding a commercial airline flights, or that bar them from flying to the United States altogether, intelligence officials said.