CAIRO, Egypt — Al-Qaida posted a video today showing what it claimed to be an insurgent attack on a military position of U.S. and Afghan forces in southern Afghanistan.

The video appears to be an attempt by the terrorist network to disparage U.S. claims to be winning the war against the Taliban and allied militia in Afghanistan. It argues that the people of Afghanistan support the insurgents and provide physical assistance to their attacks on U.S.-Afghan forces.

The tape begins with the deputy leader of al-Qaida, Ayman al-Zawahri, ridiculing President Bush's claim to have deprived al-Qaida of a safe haven in Afghanistan, calling it a "barefaced lie."

Al-Zawahri, who speaks in Arabic with an English translation in subtitles, seems to be referring to a Bush speech on Jan. 10 when the president said that U.S. forces "took away al-Qaida's safe haven in Afghanistan — and we will not allow them to re-establish it in Iraq."

With a narrator speaking in American-accented English, the tape then shows video film of what it claims is an attack on a military position in Arghandab, a district in Zabul province, 100 miles northeast of the southern city of Kandahar.

The narrator, who sounds like the American al-Qaida member Adam Gadahn, claims that the position is "liberated" by the insurgents. However, the film does not show the insurgents capturing the target — a compound of mud-plastered buildings in a valley — during the nighttime battle. It only shows the insurgents walking through the compound in daylight.

When asked about the video, the district chief of Arghandab, Fazel Bari, said the only recent clash in that area was last month when NATO-led troops and Afghan forces were ambushed by suspected Taliban militants on the road between Arghandab and Qalat, the provincial capital.

Bari said the NATO and Afghan troops suffered no casualties, but they detained one man after the battle, which ended with the Taliban retreating.

The authenticity of the scenes shown could not be verified. The video carried the logo of the al-Qaida media production company, as-Sahab, and it was posted on an Islamic Web site known for hosting extremist material.

The video shows the insurgents firing at the alleged post but their weapons cannot be discerned because it is night. Tracer bullets cross the sky, fire is returned and one sees explosions of what are said to be rocket-propelled grenades.