Officials: 'Credible Intelligence' on Terror Attack Planning Against U.S.

A handout released to Reuters by IntelCenter shows members of Somalia's Islamist rebel group al Shabaab in Mogadishu Jan. 1. (Reuters Photo)

Credible intelligence has emerged that Al Qaeda in the Arabian Peninsula is plotting another attack against the United States and U.S. interests abroad, a senior U.S. counterterrorism official confirmed to Fox News on Thursday.

The intelligence is described as not specific about time, place or method of attack, but is being taken seriously, according to this official.

The new information does not come from 23-year-old Nigerian Umar Farouk Abdulmutallab, who allegedly tried to bring down flight 253 on Christmas Day.

According to those familiar with the intelligence, the strategic threat from Al Qaeda in the Arabian Peninsula, based in Yemen, has intensified and the group is emboldened by the failed Dec. 25 plot.

"The threat did not end on Christmas Day", according to one source familiar with the intelligence.

Al Qaeda in Yemen and the Al Qaeda affiliate in Somalia, known as Al Shabaab -- translated as Mujahadeen Youth -- are described as having "shared interests and shared goals."

U.S. counterterrorism officials say clear connections now can be traced between the two terrorist groups and they are not ruling out the possibility that they are working together to attack U.S. interests.

U.S. officials also remain concerned about two dozen Somali Americans who disappeared into the Al Shabaab training camps in Somalia in the last 18 months. Their American passports would allow them to reenter the United States.

Federal authorities have information about "certain people" they are tracking, but officials would not be more specific. A U.S. counterterrorism source said authorities believe the 20 or so operatives Abdulmutallab referred to in his questioning by the FBI would not necessarily fit the same profile as the Nigerian suspect.

In addition, American cleric Anwar al-Awaki, now living in Yemen, "has moved up the terrorist supply chain," according to officials. He is now a facilitator, recruiter and operational planner.

Al-Awlaki's ascent is due to his growing confidence and ability to "spot talent" as he apparently did with Abdulmutullab. It is not due to a "leadership vacuum" within the group, officials said.

Fox News' Catherine Herridge, Justin Fishel and Mike Levine contributed to this report.