US President Barack Obama on Thursday announced some more steps to defend the nation against terrorism threats, in response to a failed bombing plot against a US international flight on Christmas Day.

US President Barack Obama makes statements to outline steps the US government is taking to try to shore up airline security, at the White House in Washington January 7, 2010. [Xinhua/Reuters Photo]

"Today, I'm directing a series of additional corrective steps across multiple agencies," Obama said at the White House in a live televised speech.

The speech was delivered as the Obama government wrapped up reviews on the terrorist watch list and aviation security after a Nigerian trained and equipped by al-Qaeda carried an explosive device onto a US international flight and attempted to set it off on Dec. 25.

Obama pointed out mistakes made in three ways led up to the potential disaster that could have cost 300 lives, which included intelligence community's failure to follow up a particular streams of intelligence related to a possible attack, a larger failure of analysis of intelligence, and ineffective terror watch list that allowed the suspected Nigerian to board the plane from the Netherlands to the United States.

Measures in four areas will be adopted to prevent such attack attempts from happening again, said the president, in addition to the three steps he had announced on Tuesday.

He directed the US intelligence community to begin assigning responsibilities for investigating all leads "on high-priority threats," and distribute the intelligence reports more rapidly and widely.

He also called for strengthened capability in analyzing, integrating and processing intelligence, and ordered to improve the criteria used to add individuals to the terrorist watch lists, especially no-fly list.

"So taken together, these reforms will improve the intelligence community's ability to collect, share, integrate, analyze and act on intelligence swiftly and effectively," he said. "In short, they will help our intelligence community do its job even better and protect American lives."

In the meantime, Obama underlined the need to invest in new systems and technology as well as strengthen international partnership to improve security screening at airports across the world.

As head of the state, Obama said that he would not "pass out blame," and took responsibility for the security mistakes leading to the Christmas bombing plot.

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

He also directed all concerned agencies' heads to establish internal accountability reviews and national security staff to monitor their efforts, saying "all of these agencies and their leaders are responsible for implementing these reforms, and all will be held accountable if they don't."

Challenged by the al-Qaeda's active recruit in the Middle East, Africa and other places, Obama said that his national security team is mapping out a strategy to contain the terrorist group's influence.

It was the second public speech Obama made this week on the Christmas incident.

On Tuesday, he announced several measures taken to enhance air security and mend the hole in the US intelligence system, including improving the terror watch list and no-fly list system, and requiring US embassies and consulates to include current visa information in their warning on individuals with terrorist or suspected terrorist connections.

The Transportation Security Administration is also demanding enhanced screening for international travelers bound for the United States, especially those from or flying through nations on the US "State Sponsor of Terrorism" or other "countries of interest" lists, he said, adding that some more measures would be made public in the days ahead.