Hussein al-Attas, 24, pleaded guilty to seven counts of making false statements.
A French citizen of Moroccan descent, Moussaoui is the only person charged with conspiring to help 19 hijackers who plunged two passenger jets into the World Trade Center, a third into the Pentagon and a fourth into a field in Pennsylvania.
Moussaoui was arrested last summer after administrators at the Minnesota flight school became suspicious of his intense desire to fly jumbo jets even though he had poor flying skills.
Al-Attas, born in Riyadh, Saudi Arabia, to Yemeni parents, was Moussaoui's friend and, briefly, his roommate in Norman, Oklahoma, where Moussaoui had come to enroll at the nearby Airman Flight School.
Al-Attas, told U.S. District Judge Michael Mukasey that he lied to investigators in Minnesota on Aug. 18 and in Oklahoma on Sept. 11, especially about Moussaoui, whom he knew by an alias.
"When the agents asked if I (also) knew his real name, I lied and said I did not," he said.
Al-Attas admitted he also lied about their plans to go to New York City in late August, 2001; knowledge of Moussaoui's desire to participate in jihad; a planned trip to Pakistan to speak to religious scholars and "others who believe that our religion favors participation in jihad."
He said he also tried to prevent law enforcement authorities from learning about some of Moussaoui's classmates at an Oklahoma flight school.
"I did not want to say anything that would cause problems for anyone else," he said.
He also admitted lying about plans to attend classes at the University of Oklahoma and his visit to a range to practice firing a handgun at a target.
Federal agents arrested Moussaoui and al-Attas in Eagan, Minn. on Aug. 16. Moussaoui had completed less than two days of classes.
Al-Attas, who is not charged with participating in or having advance knowledge of the Sept. 11 attacks, has consented to be held as a material witness in the government's conspiracy case against Moussaoui in Alexandria, Virginia. Al-Attas' lawyer said he would testify if requested.
"He is a fairly naive man who was trying to help the wrong person at the wrong time," said defense lawyer Alexander Eisemann.
Moussaoui attempted to plead guilty last Thursday to conspiring in the Sept. 11 attacks but a federal judge gave him a week to reconsider.
Eisemann told reporters that Moussaoui's attempt to plead guilty had no impact on his client's admissions. He said that plea negotiations had been under way for several months.
U.S. District Judge Michael Mukasey set Sept. 4 sentencing hearing for al-Attas. Prosecutors said in plea agreement papers that the federal sentencing guidelines recommend zero to six months prison time. Al-Attas has been in custody since September 11.
Eisemann told reporters his client had met Moussaoui at a mosque in Norman, Oklahoma, where Moussaoui was attending flight school. He said al-Attas, who was an engineering student at the University of Oklahoma, had shared an apartment with Moussaoui and at least one other person for several weeks.
The lawyer said that Moussaoui had told al-Attas he was going to flight school because his uncle was in the aviation industry.
He said that Moussaoui asked al-Attas to go with him to visit New York, Colorado and possibly Los Angeles. Eisemann said the two decided just to visit New York and return to
Eisemann was asked what his client thought the purpose of the trip was. "Mr. Moussaoui wanted to see sights in America and Mr. al-Attas was going along for the ride," he said.