US officials say they are confident, but not certain, missing Californian Adam Gadahn is the man who threatened al-Qaeda attacks in a recent video.
Officials say the man in this video is Adam Gadahn
The man appeared with his face covered in a tape shown by ABC News last month, calling himself Azzam the American and claiming to belong to al-Qaeda.
Adam Gadahn has not been linked to any specific terror activities, but the FBI says it wants to question him.
In May, he was put on an FBI list of wanted suspects.
Officials concluded after technical analysis of the tape that the speaker was Mr Gadahn, who left California for Pakistan six years ago, US networks reported.
Among other steps, intelligence officials compared the voice of Azzam to footage of a teenage Gadahn discussing environmental projects nearly 10 years ago on cable television in California, ABC says.
They also spoke to his family and showed the tape to captured al-Qaeda operatives.
However, officials say they cannot be absolutely certain of the speaker's identity.
The man on the tape threatened new attacks on the US.
"After decades of American tyranny and oppression, now it's your turn to die.
"Allah willing, the streets of America will run red with blood matching drop for drop the blood of America's victims."
FBI Director Robert Mueller said Adam Gadahn was known to have performed translations for al-Qaeda and was associated with al-Qaeda leader Abu Zubaydah in Pakistan.
He is also thought to have later trained at an Islamic militant camp in Afghanistan.
Adam Gadahn was born Adam Pearlman in 1978, the son of a 1960s psychedelic musician.
He was raised in Orange County on a goat farm, ABC says.