A former roommate of confessed Al Qaeda terrorist Zacarias Moussaoui told FBI agents that Moussaoui had expressed an interest in holy war and believed Muslims were within their rights to kill infidels, according to court testimony.

A videotaped deposition of Hussein al-Attas, who roomed with Moussaoui in 2001 in Oklahoma and was with Moussaoui in Minnesota in August 2001 when he was arrested by federal agents, was to be played for the jury Tuesday when Moussaoui's death-penalty trial resumes.

The jury got a preview of some of al-Attas' statements through the testimony Monday of Harry Samit, the FBI agent who arrested Moussaoui in August 2001 and also interrogated al-Attas.

Samit testified that his belief that Moussaoui was a radical Islamic extremist bent on terrorism was based in part on al-Attas' statements.

Al-Attas told Samit that Moussaoui often talked about jihad, or holy war, and that Moussaoui once pointed out to him a television report about Usama bin Laden, with Moussaoui noting that bin Laden was an important person.

Samit testified that he worked obsessively after Moussaoui's Aug. 16, 2001, arrest to convince FBI headquarters that Moussaoui warranted a full-scale investigation and that a search warrant should be obtained for his belongings.

The agent obtained a search warrant only after the Sept. 11 attacks, and attributed the FBI's failure to launch a timely investigation to "criminal negligence" and careerism by certain agents in FBI headquarters. The bureau's failures thwarted an opportunity to prevent the attacks, he said.

Moussaoui is the only person charged in this country in connection with the Sept. 11 attacks.

He has already pleaded guilty to conspiring with Al Qaeda to hijack aircraft and commit other crimes. But he denies a specific role in 9/11. His sentencing trial will determine his punishment: death or life in prison.

The FBI's actions between Moussaoui's arrest and Sept. 11 are crucial to the trial because prosecutors allege that Moussaoui's lies to Samit prevented the FBI from thwarting or at least minimizing the Sept. 11 attacks. Prosecutors must prove that Moussaoui's actions caused the death of at least one person on 9/11 to obtain a death penalty.

The defense argues that nothing Moussaoui said after his arrest would have made any difference to the FBI because its bureaucratic intransigence rendered it incapable of reacting swiftly to Moussaoui's arrest under any circumstances.