Abdullah, now 25 and back in his homeland of Yemen after his deportation from the United States in May, called the report "propaganda" and said he is the victim of U.S. investigators looking for someone to blame. He said he had no inkling in the summer of 2001 that two friends, Khalid Almihdhar and Nawaf Alhazmi, were about to take part in the deadliest terrorist assault on U.S. soil.

"If I could have done anything to prevent this heinous attack from happening, I would have done it," Abdullah said in a telephone interview with The Washington Post arranged by his attorney last week. "I was going to school, I was working, I was building my own future over there. I considered it my own land, and that’s how I behaved towards it. . . . I was quite happy living in America until this happened."

The comments stand in stark contrast to the 567-page commission report, which portrays Abdullah as perhaps the most suspicious acquaintance to befriend two of the hijackers during their time in Southern California. While the commission largely absolves other hijacker associates of wrongdoing, it casts Abdullah as a central figure in the hijackers’ San Diego stay and strongly suggests that he may have been an al Qaeda operative placed there to help the plot.

"Abdullah . . . is fluent in both Arabic and English, and was perfectly suited to assist the hijackers in pursuing their mission," according to the report. It adds later that "Abdullah has emerged as a key associate of" Alhazmi and Almihdhar in San Diego.

Abdullah’s story highlights one of the enduring debates of the Sept. 11 attacks: how the terrorists managed to train for the assaults, conduct surveillance and accomplish their mission — all, apparently, without assistance in the plot from anyone in the United States. The FBI, after an exhaustive check of possible accomplices, including Abdullah, supports that scenario. Others, including the commission and a House-Senate inquiry panel, have challenged the FBI’s conclusion.

Abdullah said he offered his hijacker friends no assistance with the plot and does not know anyone who did.

Abdullah, whose English is sprinkled with American colloquialisms after six years of living in the United States, said he "was very surprised" the commission "even brought me up."

"I was in custody for nearly three years and no one came up to me and said, ‘Hey, we think you were involved,’ " he said. "This has got me very upset. It is very unfair, and it’s ruining my life."

Abdullah’s San Diego attorney, Randall B. Hamud, said his client remains a virtual captive in Yemen’s capital, Sanaa, where he is under constant surveillance by the government.

Abdullah was arrested as a material witness in late September 2001. He spent 32 months in U.S. jails and prisons as the FBI and the Justice Department investigated his ties to Almihdhar, Alhazmi and a network of immigrant friends, all of whom congregated around the Rabat mosque in a suburb of San Diego.

Commission investigators complained that they were never able to interview Abdullah before he was deported. Abdullah refused to cooperate, and the Justice Department declined to grant him immunity from prosecution to compel his cooperation. The panel also is critical of the government’s decision to allow Abdullah’s deportation, arguing that unanswered questions about his case require further examination.

Abdullah’s first alleged contact with Alhazmi and Almihdhar came in February 2000. According to the commission, he may have driven them from Los Angeles to San Diego. Abdullah denies it. The two would-be hijackers sought out another person they had met recently in Los Angeles, Omar Bayoumi, at the Islamic Center of San Diego.

The hijackers later found their way to the Rabat mosque, a humble building nestled amid palm trees and ranch homes in La Mesa, 10 miles from the well-established and, by reputation, more moderate Islamic Center of San Diego. On a recent Friday, as families crowded the Islamic Center, the Rabat mosque appeared almost abandoned, its gates locked and mailbox overflowing. (A radical Yemeni imam at the Rabat mosque in 2000, Anwar Aulaqi, would later lead the Dar al Hijra mosque in Falls Church, which Alhazmi attended.)

Until the commission report, Bayoumi had been the primary focus of speculation about potential Sept. 11 accomplices in San Diego and was identified as an alleged al Qaeda associate and Saudi spy by a congressional inquiry in 2003. The Sept. 11 commission, by contrast, found "no credible evidence that he believed in violent extremism" and concluded that Bayoumi was an "unlikely candidate" to be involved in an al Qaeda plot.

Abdullah, the report strongly suggests, is a more likely accomplice.

According to the commission report, which cites FBI interviews and other investigative material, Abdullah admitted that he knew Alhazmi and Almihdhar were extremists and that Almihdhar had been involved with the Islamic Army of Aden, a group linked to al Qaeda. The report also says Abdullah "clearly was sympathetic to those extremist views."

When he was detained as a material witness after the 2001 attacks, the commission says, FBI agents found a notebook in his possession that had been written by someone else but described "planes falling from the sky, mass killing and hijacking." The report also says Abdullah showed hatred toward the U.S. government and made the statement about the attacks being brought upon the United States.

In the interview, Abdullah strenuously disputed those characterizations. He said that he had no idea Alhazmi and Almihdhar "had associations with any group or had evil plans towards the United States," and that he is "committed to my religion but not to the point of extremism at all."

The commission is particularly alarmed by reports earlier this year from two inmates housed with Abdullah in the California prison system, who alleged that Abdullah told them in the fall of 2003 "that he had known" Alhazmi and Almihdhar "were planning a terrorist attack." The two inmates’ stories are not consistent, however.

In one version, Abdullah bragged that he had been told that the two hijackers were part of an attack before they arrived in the United States. In the other, Abdullah allegedly said that he was told of the plot after Alhazmi and Almihdhar arrived in San Diego and that the hijackers "invited him to join them on the plane." The second inmate also said that Abdullah claimed to have found out about the attacks three weeks in advance.

The panel noted evidence that Alhazmi, who had left San Diego, may have called Abdullah about that time; that Abdullah stopped making calls from his cell phone after Aug. 25, 2001; and that friends reported "he started acting strangely." The report also recounts an unconfirmed witness account that Abdullah and others "behaved suspiciously" on Sept. 10, 2001, at a Texaco station where they worked, giving each other "high-fives" after one said, "It is finally going to happen."

One senior commission official called the findings "troubling" and said Abdullah’s case "deserves a much deeper investigation."

The Justice Department and the FBI take a different view, arguing that Abdullah’s case has been exhaustively investigated and that the claims of the two jailhouse informants, in particular, do not check out.

"The investigation to date has determined that there is no evidence to corroborate information that Mohdar Abdullah had prior knowledge of the 9/11 attacks," the FBI said in a statement. "The FBI continues an active investigation of Mohdar Abdullah and any connection to the 9/11 attacks."

One senior FBI official said there are numerous inconsistencies in the inmates’ claims and that investigators are not even certain both prisoners had close contact with Abdullah. The FBI’s Sept. 11 investigative team did not oppose allowing Abdullah to return to Yemen, the official said.

"There’s nobody who feels we’ve lost someone here," the official said.

Abdullah made no claims about prior knowledge of the attacks, he and his attorney said. They contend that the two inmates are attempting to use Abdullah’s notoriety as a "Sept. 11 detainee" to their advantage.

"It’s scurrilous for the committee to include in its report the spurious fantasies of jailhouse snitches trying to cut themselves a better deal with prosecutors," Abdullah lawyer Hamud said. If federal officials had any evidence linking Abdullah to the Sept. 11 plot, Hamud said, "you can be assured they would have prosecuted him."

Abdullah said he gave Alhazmi and Almihdhar tips on how to obtain driver’s licenses and other advice because it is "an obligation" for Muslims to help one another and because neither spoke English or knew the country well. As far as his behavior in August 2001, Abdullah said he does not remember acting strangely, "but I was under a lot of stress because of monetary issues and stuff like that." He denied taking part in any celebration at the gas station.

Abdullah had just transferred from Grossmont College in El Cajon, where he studied business administration, to San Diego State University, where he had planned to study information systems when he was arrested. Now he is living with his parents and attempting to find a job.

Abdullah said he was brought back to Sanaa under armed guard and held in a Yemeni jail for about a month after his deportation.

"I still can’t understand how this all happened to me," Abdullah said. "I had a life that was well established, and somehow they ruined it."

Staff writer Rene Sanchez in San Diego contributed to this report.