U.S. President Barack Obama says intelligence agencies had enough information to put Abdulmutallab on a no-fly list. (Charles Dharapak/Associated Press)U.S. President Barack Obama took responsibility Thursday for the failure of U.S. intelligence to stop a man from carrying explosives on a U.S.-bound plane Christmas Day and said he is ordering changes to how information on potential threats is handled.

"Ultimately, the buck stops with me," he said. "As president, I have a solemn responsibility to protect our nation and our people, and when the system fails, it is my responsibility."

Obama spoke after reviewing reports on how Nigerian Umar Farouk Abdulmutallab was able to board a plane despite being initially flagged to receive extra security screening.

Obama had earlier said the failure was not in gathering intelligence but rather in "connecting the dots."

He said Thursday he is telling the intelligence community to assign "clear lines of responsibility" for immediately pursuing leads on threats. He also said he wants to strengthen the way people are added to the terror watch list, and that those reports are shared more quickly and widely.

The U.S. Homeland Security Department issued a statement earlier Thursday saying Abdulmutallab was initially flagged to be given extra security screening after he landed in the U.S. The department said Abdulmutallab's potential extremist connections came up on a check of passengers already flying to the U.S. from overseas.

U.S. border officials screen international passengers against a watch list before flights leave for the U.S., and then check a second database once the flights are en route.

U.S. adds names to no-fly list

Since the attempted attack, the government has added dozens of names to its lists of suspected terrorists and others barred from flights bound for the United States.

This week, the Transportation Security Administration directed airlines to use enhanced screening techniques, including body scans and pat-downs, to assess U.S.-bound travellers from 14 countries considered sponsors of terrorism or "countries of interest."

No officials, for now, are expected to lose their jobs over the Christmas Day incident.

"I don't know what the final outcome in terms of hiring and firing will be," White House spokesman Robert Gibbs said Wednesday.

'System worked'?

Some Republicans and critics have called for the resignation of Homeland Security Secretary Janet Napolitano, who said after the incident that the "system worked." She later clarified that statement, saying she was referring to how the system worked after the thwarted attack.

Umar Farouk Abdulmutallab, 23, has been indicted on six charges, including attempted use of a weapon of mass destruction and attempted murder. (U.S. Marshal's Service/Associated Press)

On Wednesday, a U.S. grand jury indicted Abdulmutallab on six charges, including attempted use of a weapon of mass destruction and attempted murder.

Authorities say the 23-year-old was travelling to Detroit from Amsterdam when he tried to ignite an explosive device aboard the jet. Fellow passengers pounced on him before he could detonate the device.

The brush with disaster on the Northwest flight has provoked debate over the effectiveness of U.S. security provisions and questions about how anyone could get on a plane with explosives, especially a man already brought to the attention of U.S. officials.

The New York Times reported in late December that the government had information from Yemen before Christmas that a branch of al-Qaeda was preparing "a Nigerian" for a terrorist attack. The information did not include Abdulmutallab's name, the Times said.

Accused not on priority no-fly list

Abdulmutallab's name had, in fact, been put into a large database of suspect individuals. But he was never added to more restrictive lists that would have caught the attention of U.S. security officials, even though his father had warned U.S. Embassy officials in Nigeria about his son in November.

Deputy National Security Adviser John Brennan and Napolitano followed Obama with their reports on failures in intelligence and security related to the incident.

Brennan said intelligence fell through the cracks. He said the watch-list system is not broken, but the way the intelligence community feeds information into the system needs to be strengthened.

Napolitano said the failures in the screening process occurred at Amsterdam, and foreign airports need to step up their security efforts.

"This is an international issue, not just one about the United States," she said.

With files from The Associated Press