updated 1/3/2010 1:50:11 PM ET 2010-01-03T18:50:11

U.S. intelligence agencies did not miss a "smoking gun" that could have prevented an alleged attempt to blow up a U.S. airliner on Christmas Day, President Barack Obama's top counterterrorism adviser said Sunday.

Appearing on Sunday news talk shows, White House aide John Brennan cited "lapses" and errors in the sharing of intelligence and clues about the Nigerian man accused in the foiled attempt.

"There is no smoking gun," Brennan said. "There was no single piece of intelligence that said, 'this guy is going to get on a plane.'"

His comments came as a senior British government official revealed that British intelligence officials knew that the suspect had ties to U.K. extremists but did not consider him enough of a high risk to alert American authorities.

Officials realized about a year after Umar Farouk Abdulmutallab came to London to study in 2005 that he was in contact with Islamic extremists whose communications were being monitored, a senior government official told The Associated Press on Sunday.

"It was clear he was reaching out to radical extremists in the U.K. but there was nothing to indicate he was violent," the official said, speaking on condition of anonymity because of the sensitivity of his work. "There is a very large number of people in the U.K. who express interest in radical extremism but never turn to violence. He only pinged up on our radar because of other people we were interested in."

'Bits and pieces'
Brennan is leading a White House review of the incident. Obama has said there was a systemic failure to prevent the attack, which he said was instigated by an affiliate in Yemen of the al-Qaida terrorist network.

Obama ordered a thorough look at the shortcomings that permitted the plot, which failed not because of U.S. actions but because the would-be attacker was unable to ignite an explosive device. The president has summoned homeland security officials to meet with him in the White House Situation Room on Tuesday.

Abdulmutallab apparently assembled an explosive device, including 80 grams of Pentrite, or PETN, in the aircraft toilet of a Detroit-bound Northwest flight, then planned to detonate it with a syringe of chemicals. Passengers intervened, and the plan failed.

The 23-year-old suspect's name was known to intelligence officials, and his father had passed along his concern about the son's increasing radicalization.

"We had bits and pieces of information," Brennan said on CNN's "State of the Union." The father's warning, he said, was "one set of data."

But Brennan said other information available didn't provide the details needed to map it and attach it to Abdulmutallab.

Video: ‘System did not work’ "What we need to do as an intelligence community, as a government, is be able to bring those disparate bits and pieces of information together so we prevent Mr. Abdulmutallab from getting on the plane."

Brennan, speaking earlier on "Fox News Sunday," didn't say whether anyone is in line to be fired because of the oversights. He stood by Homeland Security Secretary Janet Napolitano, although he acknowledged she has "taken some hits" for saying that the airline security system had worked. It didn't, and she clarified her remarks to show she meant that the system worked only after the attack was foiled, Brennan said.

He said the situation was not like before the attacks of Sept. 11, 2001, when intelligence agencies failed to share tips and information that might have uncovered the plot.

He said there "were no turf battles" between agencies.

"There were lapses. There were human errors. The system didn't work the way it should have ... but there wasn't an effort to try to conceal information."

Tracking the 'journey of extremism'
In London, the British official said there were no signs that Abdulmutallab wanted to target the United States or was considering turning toward violence.

Video: Analyzing threats Even though there are no set profile characteristics to indicate whether a suspect is likely to turn violent, the overall risk a person poses can be assessed by looking their associates, travel patterns, threats and activities, the source said.

He declined to name the extremists that Abdulmutallab had contacted.

"Obviously if there was any indication that he was likely to target the U.S., we would have immediately alerted our U.S. counterparts," the official added. "But the fact is that many start on this journey of extremism and few complete it."

He said it wouldn't make sense to alert U.S. authorities to every person who showed up on the "fringes of extremism" and said Abdulmutallab's actual radicalization appeared to have come in the time he spent in Yemen.

© 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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