"There was a mix of human and systemic failures that contributed to this potential catastrophic breach of security," Obama said.
Senior U.S. officials told The Associated Press that intelligence authorities are now looking at conversations between the suspect in the failed attack and at least one al-Qaida member. They did not say how these communications with the suspect, Umar Farouk Abdulmutallab, took place - by Internet, cell phone or another method.
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.
Intelligence officials would not confirm whether those conversations involved Yemen-based radical cleric Anwar al-Awlaki, but other U.S. government officials said there were initial indications that he was involved. Al-Awlaki reportedly corresponded by e-mail with Maj. Nidal Malik Hasan, who is charged with killing 13 people at Fort Hood, Texas, on Nov. 5.
"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 in a brief statement to the media. "The warning signs would have triggered red flags, and the suspect would have never been allowed to board that plane for America."
Obama's statement showed more fire than he had shown previously about the lapses that allowed the bombing attack to take place and came after his homeland security secretary, Janet Napolitano, had to backtrack on an assertion that "the system worked" in the Detroit airliner scare.
An angered Obama called the shortcomings "totally unacceptable" and told reporters traveling with him on vacation here that he wanted a preliminary report by Thursday on what went wrong on Christmas Day, when the suspect carried explosives onto a flight from Amsterdam despite the fact the suspect had possible ties to al-Qaida.
It will take weeks for a more comprehensive investigation into what allowed the 23-year-old Nigerian to board the airplane he is accused of trying to blow up with more than 300 people aboard. Law enforcement officials believe the suspect tried to ignite a two-part concoction of the high explosive PETN and possibly a glycol-based liquid explosive, setting off popping, smoke and some fire but no deadly detonation. Abdulmutallab, charged with trying to destroy an aircraft, is being held at the federal prison in Milan, Mich.
Obama, interrupting his vacation for a second consecutive day to address the airliner attack, said, "It's essential that we diagnose the problems quickly."
"There were bits of information available within the intelligence community that could have - and should have - been pieced together," he said.
Abdulmutallab had been placed in one government advisory system, but 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 also did not result in Abdulmutallab's U.S. visa being revoked.
Officials in Yemen were investigating whether Abdulmutallab spent time with al-Qaida militants there during the months leading up to the botched bombing attack.
Administrators, teachers and fellow students at the San'a Institute for the Arabic Language, where Abdulmutallab had enrolled to study Arabic, told The Associated Press that he attended school for only the month of Ramadan, which began in late August. That has raised questions about what he did during the rest of his stay, which continued into December.
They also said he was not openly extremist, though he expressed anger over Israel's actions against Palestinians in Gaza. Officials also noted Tuesday that Amsterdam, where Abdulmutallab boarded his flight to Detroit, is one of nine locations where U.S. Customs and Border Protection officials are stationed to do additional screening on U.S.-bound passengers who have been flagged as a potential risk.
But it is unlikely Abdulmutallab would have been flagged because the Customs and Border Patrol officers do not routinely screen all passengers against the names of individuals on the Terrorist Identities Datamart Environment database, known as TIDE, which was the only place that Abdulmutallab was listed. The government put in place enhanced screening procedures for passengers after the Sept. 11, 2001, attacks on New York and Washington to catch potential terrorists. On U.S.-bound flights from overseas, CBP checks passenger names against some lists of potential terrorists, but not against all information the government keeps.
On top of that, airport security equipment did not detect the bomb-making devices and materials Abdulmutallab is accused of carrying on board the Northwest Airlines flight.
Obama said many things went right after the incident, with passengers and the flight crew subduing the man and government officials working quickly to increase security. He singled out Napolitano, backing her much-criticized comments that the attempted terror attack showed the aviation security system worked.
"As Secretary Napolitano has said, once the suspect attempted to take down Flight 253, after his attempt, it's clear that passengers and crew, our homeland security systems, and our aviation security took all appropriate actions," Obama said.
Napolitano received so much criticism for her Sunday talk show remarks that she did another round of interviews the following day to say the system did not work in preventing Abdulmutallab from getting on the plane with a bomb. But, she said, the response system did work after the man was subdued. She contends her remarks were taken out of context.
Meanwhile, Napolitano asked to meet with security and counterterrorism experts, including at least two former Bush administration officials, according to a person familiar with the meetings. On Tuesday, she met with former Bush homeland security adviser Fran Townsend and former DHS undersecretary for policy Stewart Baker, said the person, who spoke on condition of anonymity because the meeting was not on the secretary's public schedule.
Republicans are questioning Napolitano's judgment and a few have called for her resignation. The White House says her job is safe.
However, Obama said: "What's also clear is this: When our government has information on a known extremist and that information is not shared and acted upon as it should have been ... a systemic failure has occurred. And I consider that totally unacceptable."
The two reviews, which Obama said got under way on Sunday, are looking at airport security procedures and the U.S. system of terror watch lists.
"It now appears that weeks ago this information was passed to a component of our intelligence community but was not effectively distributed so as to get the suspect's name on a no-fly list," Obama said.
Baldor reported from Washington. Associated Press writers Audrey McAvoy in Kaneohe Bay, Hawaii, and Eileen Sullivan in Washington contributed to this report.