US security agencies had enough intelligence to disrupt a plot to blow up a plane last month, but failed to act, President Barack Obama has said.
The intelligence community had failed to "connect the dots", Mr Obama said, adding: "That's not acceptable, and I will not tolerate it."
Enhanced airport screening and a review of the US watch-list system were ordered after the 25 December attempt.
A Nigerian man known to US officials has been charged over the alleged plot.
Umar Farouk Abdulmutallab, 23, later gave "actionable" intelligence to US officials, the White House said.
His name was in a US database of about 550,000 suspected terrorists, but was not on a list that would have subjected him to additional security screening or kept him from boarding the flight to Detroit.
Mr Abdulmutallab was allegedly trained in Yemen - a country that has come under increased scrutiny from the US since his arrest.
The US suspended the repatriation of Yemeni prisoners from its Guantanamo Bay detention centre in the wake of the plot, but Mr Obama reiterated that he would push on with his plan eventually to close the prison.
Mr Obama spoke on Tuesday after being briefed on security reviews ordered after Mr Abdulmutallab's arrest.
Secretary of State Hillary Clinton, Defence Secretary Robert Gates, Homeland Security Secretary Janet Napolitano, CIA Director Leon Panetta and FBI Director Robert Mueller were among those who attended the security meeting in Washington.
In his remarks, Mr Obama said the US intelligence community had known of "red flags" indicating plans by al-Qaeda in the Arabian Peninsula to strike US targets in Yemen and the US.
He said officials now knew that al-Qaeda had been working with Mr Abdulmutallab.
"But our intelligence community failed to connect those dots, which would have placed the suspect on the no-fly list.
"In other words, this was not a failure to collect intelligence, it was a failure to integrate and understand the intelligence that we already had."
He had stern words for the analysts and officers who had access to the information.
"I will accept that intelligence by its nature is imperfect, but it is increasingly clear that intelligence was not fully analysed or fully leveraged," he said.
Mr Obama used sharper words during the closed-door meeting, the White House said.
"This was a screw-up that could have been disastrous," it quoted him as telling officials. "We dodged a bullet but just barely."
Director of National Intelligence Dennis Blair later said US intelligence agencies had to be able to stop such attempted attacks.
"The intelligence community received the president's message today - we got it, and we are moving forward to meet the new challenges," he said.
He added that intelligence officials had made "considerable progress" in collection and analysis of information and in improving collaboration, although they needed to strengthen their ability to stop "new tactics".
Mr Blair's position was created in the wake of the 11 September 2001 attacks in the US, amid efforts to improve intelligence co-ordination.
The White House said on Tuesday Mr Obama was standing by three of his top security officials, including Mr Blair.
But the BBC's Richard Lister in Washington says that given Mr Obama's comments, it seems likely that there will be some kind of shake-up and that heads will roll.
Yemen security concern
White House spokesman Robert Gibbs told the media on Tuesday that Mr Abdulmutallab had "spent a number of hours with FBI investigators in which we gleaned usable, actionable intelligence".
The suspect began his journey in Lagos, Nigeria, and changed planes at Schiphol airport in Amsterdam, in the Netherlands.
Nigeria, Somalia and Yemen were among the 14 countries singled out by Washington for enhanced security measures for travellers, introduced on Monday.
Countries considered by the US to be sponsors of terrorism - Cuba, Iran, Sudan and Syria - were also included.
The move sparked objections by some of the states. Cuba said it had summoned the US ambassador to make a formal protest, the Associated Press news agency reported.
Since the incident, officials have moved dozens of names on to "watch" and "no-fly" lists, as they seek to overhaul security, a White House spokesman said on Tuesday.
Those on the watch-list are subject to extra security checks, while those on the no-fly list are not allowed to board flights to the US.
Yemen-based al-Qaeda in the Arabian Peninsula said last week it had trained and equipped Mr Abdulmutallab for the plane plot.
The US re-opened its embassy in Yemen on Tuesday, following what it called successful counter-terrorism operations by government security forces on Monday north of the capital.
Yemeni authorities have tightened security measures at Sanaa's airport, as well as around several other embassies.