The Nigerian man accused of trying to blow up a US airliner on Christmas Day has provided "useful, actionable" intelligence to US authorities after the FBI flew his relatives to the US to urge him to cooperate, US officials said.

Umar Farouk Abdulmutallab, 23, started talking again after FBI agents flew family members from Nigeria to help convince him to provide information on how the botched December 25 bomb plot was arranged and whether further attacks were in the works, a senior US official said, speaking on condition of anonymity.

"I'm confident he's going to continue to cooperate," the official said, although he declined to say whether Abdulmutallab had been offered a plea deal or leniency in exchange for answering questions again.

The Obama administration has been criticized by Republicans and Democrats because Abdulmutallab was interviewed by FBI agents for about an hour before he stopped cooperating and he was then read his so-called Miranda rights, providing him full US constitutional legal protections.

Prosecutors charged Abdulmutallab with trying to blow up the flight from Amsterdam to Detroit with a bomb sewn into his underwear, drawing further criticism from some lawmakers who said he should face a special military tribunal instead and questioning by intelligence operatives instead of the FBI.

"Abdulmutallab is talking and has been talking since last week providing useful, actionable and current intelligence that we've been actively following up on," a US law enforcement official said, declining to be named because the investigation is ongoing.

If convicted, Abdulmutallab could spend the rest of his life in a US prison -- a potential fate that may provide an incentive for him to cooperate with investigators.

'Fully apprised'

President Barack Obama was kept "fully apprised" on Abdulmutallab's change of heart, the senior US official said.

Obama, who has ordered reforms to prevent future security lapses such as those that occurred in this incident, had faced criticism from Republicans for waiting three days during a Hawaii vacation to comment on the attempted bombing.

Director of National Intelligence Dennis Blair told lawmakers there should be flexibility to make decisions on a case-by-case basis about whether such suspects go through a civilian or military legal process.

Before Abdulmutallab stopped talking, administration officials have said he initially provided useful information.

That included telling investigators that he had received training as well as the explosive device from militants in Yemen affiliated with al Qaeda.

The Yemen-based al Qaeda group has become a significant concern to US intelligence agencies that are monitoring its capabilities, intentions and recruitment of Westerners, Blair told the Senate Intelligence Committee.

Blair also said he was confident that gaps had been fixed since the Dec. 25 incident and that another person attempting a similar attack would be caught before getting on a plane.

"I'm confident that someone who left the trail that Abdulmutallab did would now be found," Blair said. "What I can't tell is even with these improvements we would be able to catch someone who took more care."

In an audiotape aired recently on Al Jazeera television, a man purporting to be al Qaeda leader Osama bin Laden praised Abdulmutallab and vowed more strikes at the United States.

"My greatest concern, and what keeps me awake at night, is that al Qaeda and its terrorist allies and affiliates could very well attack the United States," CIA Director Leon Panetta said at the same hearing.

The biggest threat is not necessarily another attack like the one on Sept. 11, 2001, but that al Qaeda is adapting its methods in ways often difficult to detect, he said.

Al Qaeda is trying to strike the US by deploying people to the country, and the concern is that the group will use people with "clean credentials" such as Abdulmutallab who do not have a history of terrorism, Panetta said. Abdulmutallab had a visa to enter the United States. – Reuters