WASHINGTON - President Barack Obama took ultimate responsibility on Thursday for security lapses that allowed an attempted Christmas Day bombing of a U.S. airliner and ordered reforms aimed at thwarting future attacks.

Obama outlined the measures, including tightened passenger screening and expanded terrorism watchlists, as the White House released a declassified account of what went wrong that allegedly allowed a Nigerian man to come close to blowing up a flight from Amsterdam on December 25.

With an eye to the potential political fallout over his administration's response, Obama again sought to reassure Americans he was doing everything possible to fix intelligence faults and beef up security to thwart future attacks.

I am less interested in passing out blame than I am in learning from and correcting these mistakes to make us safer. For ultimately the buck stops with me, Obama said at the White House. As president I have a solemn responsibility to protect our nation and our people, and when the system fails, it is my responsibility.

Addressing Americans about the near-disaster for the second time in three days, Obama said was ordering implementation of a series of reforms to plug the security gaps exposed by the attempted bombing, including wider distribution of intelligence and more use of body-scanning technology at airports.

The White House report ordered up by Obama detailed initial findings about the attempted bombing that authorities have blamed on Umar Farouk Abdulmutallab, 23, who has been linked to a Yemen-based branch of al Qaeda.

By releasing the review, Obama may be seeking not only to assuage public safety concerns but also minimize political damage to his administration before expected congressional committee hearings on the attempted attack.

Republicans have sought to paint the Democratic president as weak on national security issues, hoping to score political points in a midterm election year. Obama had already acknowledged a security screw-up in the December 25 incident.

With Obama just back this week from his Hawaiian vacation, counterterrorism has jumped to the top of his agenda, forcing him into a juggling act with other pressing priorities. The White House insists, however, he is not being distracted from tackling double-digit unemployment and overhauling healthcare.

(Editing by Peter Cooney)

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