The leader of al Qaeda's most dangerous affiliate is the star of a propaganda video showing an unusually large gathering of apparent militants.

Nasir al-Wahishi, believed to be the leader of al Qaeda's Yemen affiliate al Qaeda in the Arabian Peninsula (AQAP), appears in good spirits as he addresses dozens of fighters as the black flag of al Qaeda flaps in the breeze among them.

"The enemy crusader still has cards to play," al-Wahishi says in the footage. "We must remember that we are always fighting against the big enemy. We must eliminate the cross held by the cross bearer America."

The highly produced, undated video was posted online at least two weeks ago and also shows the other fighters making displays of respect to al-Wahishi.

An American official told ABC News that the U.S. intelligence community believes the video is authentic and may show a gathering of escapees from a Yemen prison.

"The depiction of such a large gathering of fighters and the appearance of senior leaders are atypical of AQAP's propaganda videos," the official said.

The U.S. State Department today reiterated that such a large gathering was "unusual," but said such high numbers of fighters, meeting in broad daylight, did not necessarily mean anything when it comes to al Qaeda's operational strength.

"I don't think we can make generalizations about their strength based on one video, quite frankly," State Department spokesperson Marie Harf told reporters. "We know they've been gaining strength."

Top U.S. officials have previously described AQAP as the most dangerous of the al Qaeda affiliates, moreso than the terror group's core cadre led by Ayman al-Zawahiri in southwest Asia.

Counted among AQAP's members is Ibrahim al-Asiri, a devious bombmaker who is suspected of constructing explosive devices hidden in printer cartridges for the failed cargo bomb plot of 2010.

The Center for Combating Terrorism Center at West Point describes al-Wahishi as a "tiny wisp of a man with a jutting beard and soft-spoken manner" who joined al Qaeda before the 9/11 terror attacks on the U.S. Al-Wahishi himself escaped from a maximum security prison in Yemen in 2006, the center said.

ABC News' Lee Ferran contributed to this report.