Over the objection of his lawyers, Moussaoui calmly admitted his guilt in a courtroom a few miles from where one of the hijacked planes crashed into the Pentagon in 2001, setting up a showdown with prosecutors who quickly reaffirmed they will seek Moussaoui's execution.
''I will fight every inch against the death penalty,'' Moussaoui told U.S. District Judge Leonie Brinkema as he became the only person convicted in a U.S. court in connection with the Sept. 11 plot that killed nearly 3,000 people.
The unshackled Moussaoui, wearing a beard and green prison jumpsuit, told the judge he had not been promised a lighter sentence for his guilty pleas. Then he added, ''I don't expect any leniency from the Americans.''
Moussaoui, a 36-year-old French citizen, pleaded guilty to six felonies, four of which carry the death penalty. They accuse him of conspiring with the 19 hijackers and al-Qaida leaders in a broad plot to kill Americans using commercial airliners as weapons. The conspiracy included the Sept. 11 attacks.
In a ''statement of facts'' compiled by prosecutors and signed Friday by Moussouai, he acknowledged knowing about the plot to fly planes into prominent U.S. buildings, then lying to federal agents after his arrest in August 2001 to avoid exposing the plot.
But in his court appearance, Moussaoui hinted at a possible death penalty defense. He tried to distance himself from the specific events on Sept. 11, saying that nothing in the statement he signed declared he was ''specifically guilty of 9-11.''
The pleas ended a three-year legal drama during which Moussaoui attempted to fire his lawyers, ranted against Brinkema and prosecutors and produced arguments over national secrets and access to captured al-Qaida leaders that reached the Supreme Court.
Before accepting the guilty pleas, Brinkema complimented Moussaoui, who in the past had derided her in handwritten court filings.
''He has a better understanding of the legal system than some lawyers I have seen in court,'' the judge said.
Prosecutors will seek to put Moussaoui to death, Attorney General Alberto Gonzales said at a news conference shortly after Moussaoui's hearing ended. ''The fact that Moussaoui participated in this terrorist conspiracy is no longer in doubt,'' he said, hailing Moussaoui's ''chilling admission of guilt.''
Moussaoui was arrested on immigration charges in August 2001 after drawing attention at a Minnesota flight school because he had said he wanted to learn to fly a Boeing 747 although he had no pilot's license. He was in custody on Sept. 11.
In contrast with previous court appearances where he angrily taunted his accusers, Moussaoui on Friday occasionally joked, calmly answered questions and described for the first time how he was being trained to fly a jet into the White House. It was not clear when that attack was to occur.
''How do you plead?'' Brinkema asked him for each of the six felony counts. Each time, he answered, ''Guilty.''
The judge asked Moussaoui to review the lengthy statement of facts in which prosecutors laid out their case against him. He appeared to carefully review it as hushed court spectators watched intently. Brinkema asked if he understood it.
''Yes, I have read more than 10 times this statement,'' he said. ''I pondered each paragraph and find it factual.''
In the statement, Moussaoui said bin Laden had personally selected him to take part in an attack on the White House with a commercial airliner.
Bin Laden told Moussaoui, ''Sahrawi, remember your dream,'' according to the statement. Abu Khaled al Sahrawi was one of the names Moussaoui used.
Brinkema asked defense lawyer Alan Yamamoto, the only attorney Moussaoui has been willing to talk to in recent weeks, if he was satisfied his client understood what he was doing by pleading guilty.
''When I have spoken to him, we have disagreed,'' Yamamoto said. ''He is facing the possibility of death or life in prison. He has told me that he understands that.''
Prosecutor Robert Spencer told the court he believed Moussaoui should be ordered to pay restitution to the Sept. 11 victims.
When the judge noted that part of the penalties could include a $250,000 fine, Moussaoui replied, ''I wonder where I will get the money.''
Before he formally entered the plea, he was asked if he understood the statement could be used against him to prove he was guilty. ''Absolutely, I do understand that,'' he said.
A few seconds later, he added, ''Where do I get the pen?''
Outside the courthouse, family members of Sept. 11 victims expressed satisfaction with the outcome and their gratitude to the government for pursuing the case.
Dominic J. Puopolo Jr. of Miami Beach, Fla., whose mother from Dover, Mass., died on American Airlines Flight 11 that crashed into the World Trade Center, said he had ''a tremendous feeling justice is being served.'' He said, ''I promised my mother shortly after she was murdered I'd somehow have justice.''
