WASHINGTON — The Nigerian airline bombing suspect was flagged for extra screening after he was already on the plane and headed for the U.S., officials said Thursday, as President Barack Obama got ready to outline government missteps in the near-catastrophe and order fixes.

The White House was to make public its account of how a suspected terrorist slipped through post-Sept. 11 security to board the plane in Amsterdam with an explosive. Obama’s national security adviser said that people who read the report will feel a “certain shock” about all the missed warning signs.

Obama was to address the U.S.about the findings Thursday. His scheduled comments were delayed twice —by two hours, and then abruptly again by an hour and a half. A White House spokesman said Obama was still finishing his remarks and that officials were still working on declassifying a version of the what-went-wrong intelligence report to e released to the public.

A government official said the president will order U.S. agencies to move faster and more accurately in adding suspects to a watch list designed to stop terrorists before they strike.

This would mean that individuals, like the suspect in the attempted bombing of the Detroit-bound airplane, with potential ties to terrorist organizations or violent extremists, would be included in the watch list more rapidly. The government’s much smaller “no-fly” list is drawn from the most worrisome names on the watch list.

It was expected that building up the lists would require additional resources.

The official, who is familiar with the president’s strategy, was not authorized to speak publicly and spoke on condition of anonymity.

Obama’s remarks Thursday follow a promise earlier in the week to disclose new steps to thwart future terror plots.

No firings over the December security debacle are expected for now.

National Counterterrorism Director Michael Leiter is at the center of the storm about intelligence failures that allowed the suspect to get on a plane in Nigeria with an undetected bomb, after training in Yemen with al-Qaida extremists. The counterterror center’s purpose is to link together the disparate pieces of intelligence that might have uncovered a bomb plot.

Leiter was at his headquarters on Christmas Day after the terrorist attempt but left on a planned family vacation the next day.

The White House defended Leiter. Denis McDonough, National Security Council chief of staff, said Leiter left only after consultations with the White House and the director of national intelligence and remained in discussions with the White House and others throughout the break.

McDonough said the travel did not affect in any way Leiter’s ability to remain engaged on the incident.

National security adviser Gen. James Jones said in an interview with USA Today that people who read the new report will “be surprised that these correlations weren’t made” between clues pointing toward a threat from Umar Farouk Abdulmutallab. Even though the 23-year-old Nigerian man was in a database of possible terrorists, he allegedly managed to fly from Nigeria through Amsterdam to Detroit with an explosive concealed on his body.

Administration officials say they had flagged Abdulmutallab as someone who should go through additional security screening upon landing. In a statement early Thursday, the department said the alleged bomber’s potential ties to extremists came up in a routine check of passengers en route to the U.S. from overseas — and not because of any suddenly gathered intelligence that emerged during the flight.

Customs and Border Protection officials screen passengers against terrorist watch lists before international flights leave for the U.S., then check names against a different database while the flight is in the air. It was during this second check that officials caught information Abdulmutallab’s father had provided to the U.S. embassy in Nigeria a month earlier, warning the U.S. that his son had drifted into extremism in the al-Qaida hotbed of Yemen.

Even if Customs and Border Protection officers gave Abdulmutallab extra scrutiny when he landed in Detroit, there was no guarantee that the information provided by his father would have been enough for an officer to decide he should not be allowed in the country.

Adbulmutallab’s name was one in about 550,000 of an intelligence database of people with suspected terrorist ties. There was not enough information about Abdulmutallab’s nexus to terrorism to get him onto a subset of the list where he would have been flagged in initial screening. An even stricter “no-fly” list contains about 3,400 names.

Among Obama’s campaign promises was to determine whether post Sept. 11 security measures are adequate for the continuing threat against airplanes. His change.gov campaign Web site noted that “airline passengers are still not screened against a comprehensive terrorist watch list.” It went on: “Such a list must be developed and used in a way that safeguards passengers’ privacy while ensuring the safety of air travel.”

For an administration rocked by the breach of security, Thursday was meant to be a pivot point from an incident that has dominated attention.

“In many ways, this will be the close of this part of the investigation,” White House press secretary Robert Gibbs said Wednesday.

The White House is eager to start moving public attention back to its efforts to expand health care and boost the economy, while careful to say Obama will be monitoring security improvements.

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Associated Press writers Pamela Hess, Eileen Sullivan and Julie Pace contributed to this report.

Murtala Mohammed Airport in Lagos, Nigeria. Nigerian Umar Farouk Abdulmutallab, who boarded there, claimed to be acting on orders from al-Qaida when he allegedly set off an explosive device on a Delta flight in a failed Christmas Day terrorist attack as his plane was landing in Detroit. Photo by The Associated Press

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