Video has emerged which appears to show the alleged Christmas Day Detroit plane bomber attending a desert training camp run by al-Qaeda in Yemen.
The video released by ABC News shows a man resembling Umar Farouk Abdulmutallab firing a rifle and making a “martyrdom” statement to camera.
Gunmen are shown firing at British, UN and Israeli flags or symbols.
Another piece of video being circulated appears to confirm a fugitive US-Yemeni cleric’s ties to al-Qaeda.
US-based monitoring group Intelcenter says the film of Anwar al-Awlaki was released by the media arm of al-Qaeda in the Arabian Peninsula (AQAP).
In it, Mr Awlaki praises both Mr Abdulmutallab and Maj Nidal Malik Hasan, the US army psychiatrist accused of killing 13 people at Fort Hood, Texas, in November. He describes both men as his “students”.
“While [Mr Awlaki] had been supportive of groups in the past, he has until now never been publicly connected to a group through its official messages,” IntelCenter said.
Mr Abdulmutallab has been in US custody since being overpowered by passengers as he allegedly tried to blow up a jet.
A US intelligence official said the preliminary judgment was that the person in the video was indeed Mr Abdulmutallab, the Associated Press news agency reports.
The footage was consistent with the understanding that he was in training, the official added, speaking on condition of anonymity.
ABC News says the video was produced by AQAP.
In the footage, the man resembling Mr Abdulmutallab accuses “the Jews and the Christians and their agents” of occupying Muslim lands, and says Muslims have the right to wage jihad (holy war) on them.
He also reads out several passages of the Koran.
Mr Abdulmutallab, a 23-year-old Nigerian, received burns from the bomb allegedly hidden in his underwear but nobody else was injured during the alleged attempt to bomb Flight 253 from Amsterdam to Detroit.
The suspect subsequently denied charges which included attempting to murder 289 people and trying to use a weapon of mass destruction.
He is said to be co-operating with US investigators, discussing his contacts in Yemen and providing intelligence in multiple terrorism investigations.