Osama bin Laden’s latest audiotape illustrates the risks of keeping the so-called 20th hijacker alive, the sister of a September 11 victim said yesterday.

“Death is the only way to ensure that Moussaoui is not used as a tool of propaganda against Americans,” Debra Burlingame, whose brother Charles was a pilot of American Airlines flight 77, which smashed into the Pentagon on September 11, 2001, said. “And this bin Laden tape is the proof.”

In an audiotape released yesterday, Mr. bin Laden defends Zacarias Moussaoui, the only person convicted by an American court for the September 11 attacks. He was sentenced to life in prison without parole on May 4.

Mr. bin Laden’s statement contradicts the court testimony of the operational commander of the September 11 attacks, Khalid Sheik Mohammed, who is in custody.

In yesterday’s tape, Mr. bin Laden denied he assigned Moussaoui to participate in the attacks. “I begin by talking about brother Zacarias Moussaoui. The truth is that he has no connection whatsoever with the events of September 11. I am certain of what I say, because I was responsible for entrusting the 19 brothers … with those raids, and I did not assign brother Zacarias to be with them.”

Mohammed’s testimony stated that Mohammed and his deputy assigned the “pilots” to the planes, not Mr. bin Laden.

Mr. bin Laden disputed the validity of Moussaoui’s confession and guilty plea. “His confession that he was assigned to participate in those raids is a false confession which no intelligent person doubts is a result of the pressure put upon him,” he said.

Mr. bin Laden contends Moussaoui could not have been part of the plot because he was not assigned “muscle” to take control of an airplane.

“The participants in September 11 were two groups: pilots and support teams for each pilot in order to control the aircraft,” he said. “And since Zacarias Moussaoui was learning how to fly, it follows that he was not the 20th person in the teams which helped to control the airplanes, as your [American] government previously claimed.

“If Moussaoui was studying aviation to become a pilot of one of the planes, then let him tell us the names of those assigned to help him control the plane, but he will not be able to do so for a simple reason: They do not exist.”

“Clearly bin Laden is trying to propagandize the Moussaoui verdict, and it only emphasizes my regret he was not put to death,” Ms. Burlingame told The New York Sun.

The bin Laden audiotape was released via a Web site frequented by Al Qaeda supporters. The CIA has not authenticated the voice to be that of Mr. bin Laden.

If the voice on the tape is Mr. bin Laden’s, it would be the archterrorist’s third message this year – a development some analysts see as a desperate bid for relevance.

Mr. bin Laden appears to be trying to prove his relevance by rushing out tapes on current events – but the tape seems to show the opposite. Moussaoui was sentenced on May 4. The 19-day gap from Mr. bin Laden’s lips to an extremist Web site suggests he is in a remote area.

It is too soon to tell if the latest tape contains any hidden messages, a CIA spokesman said. It does not contain any overt threats.