The tape on Wednesday showed a man sitting behind a wooden desk as three men pointed their guns towards him.
He was holding what looked like a passport and a photo identification.
In the video broadcast, US contractor Jeffrey Ake pleaded with the US administration to open a dialogue with the "Iraqi resistance" and to work towards saving his life.
Appearing in the tape aired by Aljazeera two days after his abduction, the American also urged US forces to pull out of Iraq.
Aljazeera said the statements appeared to have been made made under abnormal circumstances.
The US embassy spokesman in Baghdad - Bob Callahan - confirmed the captive's name as Jeffrey Ake and that the pictures seemed to be consistent with his appearance, but declined to give further details.
No group has claimed responsibility for the abduction.