A spokesperson for the unidentified Iraqi resistance group said on the tape the soldier was being "treated according to the Islamic way of treating prisoners of war".
He added the group had arrested the soldier in order to swap him with some of its hostages held by the American occupying forces.
The videotape, received late on Friday, showed the captive dressed in US army uniform and surrounded by armed masked men. On the tape, the soldier identifies himself as Keith Mathew Maupin.
An international legal expert, Dr Abd Allah al-Ashal, told Aljazeera Maupin ought to be treated as a prisoner of war since the US had acknowledged it was the occupying power and the Geneva Conventions were applicable.
US studies tape
The US military received a copy of the tape on Friday. A US defence official said the videotape had been received by the military in Iraq.
"We are, of course, looking at the tape," said the official.
An increasing number of foreign civilian construction and
aid workers have been seized in Iraq this month, with
their captors demanding that countries such as Japan and Italy pull out their troops from the war-torn country.
At least one of the hostages, an Italian civilian, was murdered.
One other US soldier, Sgt Elmer Krause, 40, of Greensboro, North Carolina, is officially listed as missing.