President Barack Obama is to receive a preliminary report Thursday on how a 23-year-old Nigerian with suspected terrorist ties managed to board a plane he is accused of attempting to bomb on Christmas Day, along with recommendations on how to prevent a sequel.

The report is just the first step in what is shaping up to be an Obama-led effort to change the nation's intelligence practices after an attack that failed not because of U.S. anti-terrorism policies, but despite them. Administration officials said the system to protect the nation's skies from terrorists was deeply flawed and, even then, the government failed to follow its own directives.

White House homeland security and counterterrorism adviser John Brennan was scheduled to send Obama a first summary of the nation's efforts to track more than half a million potential terrorists. Officials said it was unlikely Obama would speak publicly about the report, although the vacationing president probably would talk several times throughout the day with his national security team.

Obama has demanded answers on why the U.S. intelligence community never pieced together information that could have prevented Umar Farouk Abdulmutallab, charged with trying to destroy a Detroit-bound airliner, from ever getting on the plane. Obama called the situation "totally unacceptable" when he met with reporters Tuesday and put his top intelligence officials on notice that he wanted changes.

Administration officials have spent the last week poring over reams of data, looking for failings that allowed Abdulmutallab to board the Northwest Airlines flight from Nigeria by way of Amsterdam. Officials have been sending details to Brennan, who has emerged at the center of the review.

Al-Qaida in the Arabian Peninsula, an offshoot of Osama bin Laden's group, claimed it was behind the attempt to bomb the Northwest airliner.

Senior U.S. officials told The Associated Press that intelligence authorities are looking at conversations between the suspect in the failed attack and at least one al-Qaida member. The officials, who spoke on condition of anonymity to discuss intelligence matters, said the conversations were vague or coded, but the intelligence community believes that, in hindsight, the communications may have been referring to the Detroit attack.

Officials said the link between the suspect's planning and al-Qaida's goals was becoming clearer as the review progressed.

"There were bits of information available within the intelligence community that could have _ and should have _ been pieced together," Obama said earlier this week.

The goal now, officials say, is to do everything the U.S. can to prevent a repeat. Even so, they acknowledge a perfect system is impossible to create and it will take weeks to complete a more comprehensive investigation.

Abdulmutallab had been placed in one expansive database, but he never made it onto more restrictive lists that would have caught the attention of U.S. counterterrorist screeners, despite his father's warnings to U.S. Embassy officials in Nigeria last month. Those warnings did not result in Abdulmutallab's U.S. visa being revoked.

"Had this critical information been shared, it could have been compiled with other intelligence, and a fuller, clearer picture of the suspect would have emerged," Obama said. "The warning signs would have triggered red flags, and the suspect would have never been allowed to board that plane for America."

U.S. investigators said Abdulmutallab told them he received training and instructions from al-Qaida operatives in Yemen. Yemen's government has said Abdulmutallab spent two periods in the country, from 2004 to 2005 and from August to December of this year, just before the attempted attack.

The U.S. has increasingly provided intelligence, surveillance and training to Yemeni forces during the past year, and has provided some firepower, according to a senior U.S. defense official, who requested anonymity because he was not authorized to discuss the subject.

Republicans _ from the top Republican on a House intelligence panel to former Vice President Dick Cheney _ have criticized the delay between the attack and the president's first statement. On the White House blog, communications director Dan Pfeiffer decried Cheney for injecting politics into what the administration is treating as a terrorist attack.

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Associated Press writers Eileen Sullivan and Lolita C. Baldor in Washington contributed to this report.