Al-Jazeera television received a video yesterday that militants said showed the execution of an American soldier who had been taken hostage in April, but U.S. military officials said the camera angle made it impossible to be certain of the victim's identity.

U.S. military officials said they had notified the family of Pfc. Keith M. Maupin of Batavia, Ohio, that the videotape had surfaced, but told them they did not know whether Maupin was the man shown.

Al-Jazeera said yesterday that it had received the video along with a statement from an Iraqi militant group, which said it had killed the soldier because the U.S. government had not changed its policies in Iraq.

The network aired a portion of video showing a blindfolded man sitting on the ground who was identified as Maupin in the accompanying statement, the Associated Press reported from Baghdad. Al-Jazeera said that in the next scene, gunmen shoot the man in the back of the head, in front of a hole dug in the ground, according to AP, which said the station did not broadcast the killing.

U.S. military officials said they had seen the tape within the past 24 hours.

Lt. Col Pamela Hart, an Army spokeswoman at the Pentagon, said the videotape appeared to show a U.S. soldier being shot in the head, but that it was unclear who the victim was, or whether the tape was genuine.

Other government officials said the man on the tape may be Maupin, but that they could not be sure. "We cannot be 100 percent certain," said one official, because the video was shot from behind the man and did not show his face.

Maupin was assigned to the Army Reserve's 724th Transportation Company, based at Bartonville, Ill. He was one of two soldiers and seven contractors who were traveling in a fuel-truck convoy on April 9 when they were ambushed with gunfire and rocket-propelled grenades in a western suburb of Baghdad.

Bodies of four of the contractors were later found, as was the body of the second soldier, Sgt. Elmer C. Krause of Greensboro, N.C. One of the contractors, Thomas Hamill of Macon, Miss., later escaped from his captors and returned home.

Maupin and two others have been missing since then, though Maupin was shown in a video broadcast on Arab television on April 16.

The video showed a soldier, who gave his name as Keith Matthew Maupin, squatting on the ground, surrounded by six masked men, several of them with rifles. He appeared unharmed.

The new videotape received by al-Jazeera contained some of that previously shown footage, U.S. officials said. Hart said U.S. military officials overseas and in the United States were studying the new tape for evidence, and that Army officials continued to work with Maupin's family.

Staff writers Josh White and Thomas E. Ricks contributed to this report.

An al-Jazeera image on April 16 shows a U.S. soldier who says he is Keith Matthew Maupin. A new video allegedly shows his execution.