CAIRO, Egypt — The latest tape purportedly released by Osama bin Laden may be an attempt by the al-Qaida chief to regain his pre-eminence in the global terror network and raise his profile overall after being sidelined by insurgents in Iraq, terrorism experts said today.

In an audio tape posted on the Internet late Tuesday, a speaker claiming to be bin Laden said that neither Zacarias Moussaoui — the only person convicted in the United States for the Sept. 11 attacks — nor anyone held at Guantánamo had anything to do with the al-Qaida operation.

"I am the one in charge of the 19 brothers and I never assigned brother Zacharias to be with them in that mission," he said, referring to the 19 men who hijacked the four aircraft used in the Sept. 11, 2001, attacks.

Two counterterrorism officials in Washington, who spoke on condition of anonymity, said U.S. intelligence is aware of the bin Laden message. One of the officials said there is no reason to doubt its authenticity.

If authentic, it would be the third tape that bin Laden has issued this year — a sharp increase in the volume of propaganda issued by al-Qaida since August, according to terror experts such as Ben Venzke, head of IntelCenter, a private U.S. company that monitors militant message traffic and provides counterterrorism intelligence services to the U.S. government.

"Al-Qaida messaging volume levels are at the highest now than at any point since the group's inception," Venzke said.

Rohan Gunaratna of the Institute of Defense and Strategic Studies in Singapore said the increase in propaganda was apparently bin Laden's attempt to compensate for his group's loss of ability to mount attacks. The U.S.-led war on terror apparently has severely disrupted the portion of al-Qaida directly under bin Laden's control, he said.

That has allowed the head of al-Qaida in Iraq, Abu Musab al-Zarqawi, to capture the spotlight on the world terrorism stage watched by militant sympathizers, Gunaratna told The Associated Press in a call from Singapore.

"The jihadis are increasingly looking to al-Zarqawi, who is on the ground and every day is killing Americans in Iraq," Gunaratna said. "Al-Zarqawi is stealing the thunder of bin Laden."

By stepping up his propaganda, Gunaratna said he believed "bin Laden is trying to maintain his leadership in the global jihad."

Moussaoui, a 37-year-old Frenchman and admitted al-Qaida member, was sentenced to life in prison earlier this month after a jury in the United States ruled that he was responsible for at least one death on Sept. 11.

On the tape, bin Laden said to Americans: "Since Zacarias Moussaoui was still learning how to fly, he wasn't No. 20 in the group, as your government has claimed."

Bin Laden said Moussaoui's confession of involvement in Sept. 11 was "void," and the result of pressure during imprisonment.

"Brother Moussaoui was arrested two weeks before the events, and if he had known something — even very little — about the Sept. 11 group, we would have informed the leader of the operation, Mohammad Atta, and the others ... to leave America before being discovered," bin Laden said.

Bin Laden also said that none of the hundreds of terror suspects held at the U.S. prison at Guantanamo Bay, Cuba, was involved in the Sept. 11 attacks — and said most had no ties to al-Qaida.