(CBS) The Justice Department will seek the death penalty for Zacarias Moussaoui if a jury finds the French citizen guilty of conspiring to kill thousands of people in the Sept. 11 terror attacks, according to court papers filed Thursday.

Attorney General John Ashcroft rejected pleas from the French Justice Ministry not to seek a death sentence for Moussaoui, the only person charged in the United States for direct involvement in the Sept. 11 attacks.

Ashcroft accepted the recommendation of his prosecutors in the case.

"The government will seek the sentence of death, in that the circumstances of the offenses are such that a sentence of death is justified," prosecutors said in the eight-page court filing.

They said Moussaoui's actions resulted in the deaths of about 3,000 people, the largest loss of life stemming from a criminal act in U.S. history, and they added he "has demonstrated a lack of remorse for his criminal conduct."

Moussaoui, 33, a French citizen of Moroccan descent, is charged with conspiring with Osama bin Laden, the hijackers and others to commit the Sept. 11 attacks. His trial is to begin Sept. 30. Four of the six counts brought against Moussaoui carry a maximum sentence of death.

In anticipation of a guilty verdict, CBS News Correspondent Jim Stewart reports that prosecutors have begun soliciting Sept. 11 relatives for stories about their loved ones. The 30 most compelling would testify at a sentencing phase that might also include displaying photographs of the dead and replaying their last messages on phone answering machines.

Carrie Lemack, who lost her mother on American Airlines Flight 11, has volunteered.

"It allowed us to talk about our families, my sisters and I to talk about our Mom, and how much she meant to us and how we loved her," she said.

"The defendant, Zacarias Moussaoui, intentionally participated in an act contemplating that the life of a person would be taken or intending that lethal force would be used ... and the victims died as a direct result of the act," U.S. Attorney Paul J. McNulty said in the filing.

The document charged that Moussaoui engaged in an act of violence "knowing that the act created a grave risk of death to a person" and that "the crime constituted a reckless disregard for human life."

The government said in its court filing that it would seek to prove that Moussaoui committed the offenses "in an especially heinous, cruel and depraved manner in that they involved torture and serious physical abuse to the victims."

The offenses were committed "after substantial planning and premeditation to cause the death of a person and to commit an act of terrorism," the government argued.

France said it regretted the decision to seek the death penalty and that it would not supply evidence that could lead to such a sentence.

Justice Minister Marylise Lebranchu, whose country got rid of the death penalty 20 years ago, said legal cooperation with Washington would continue in the aftermath of the Sept. 11 attacks, but that France would move cautiously from now on.

"I regret this decision, but we remain supportive of the United States after what happened," Lebranchu told reporters. "Everybody in France remains supportive."

"We shall continue judicial cooperation. However, under no circumstances shall we transmit a piece of evidence if it could be used to back up a death sentence," she said. "We shall be careful about the way we implement this cooperation.

Before his arrest, Moussaoui attended U.S. flight schools and "enjoyed the educational opportunities available in a free society, for the purpose of gaining specialized knowledge in flying an aircraft in order to kill as many American citizens as possible," the document said.

The government described the effects of the attacks as "the largest loss of life resulting from a criminal act in the history of the United States."

The government, describing the destruction caused when two of four hijacked jetliner crashed into the World Trade Center in New York, said the attacks caused the deaths of:

343 members of the New York City fire department, including the majority of its upper management and the loss of 92 pieces of equipment.

37 Port Authority police officers and 38 Port Authority civilian authorities.

23 New York City police officers.

The attacks also destroyed two major government law enforcement offices.

In court papers, prosecutors accused Moussaoui of some of the same activities as the Sept. 11 hijackers by taking flight training in the United States, inquiring about crop dusting and purchasing flight-deck training videos.

Moussaoui received money in July and August from Ramzi Bin al-Shibh, an alleged member of a German terrorist cell who was a roommate of Mohammed Atta, the suspected ringleader in the attacks, the indictment said. The FBI contends Bin al-Shibh may have been planning to be the 20th hijacker.

The indictment also alleged that Moussaoui attended an al Qaeda camp in Afghanistan and by the end of September 2000 was making moves similar to some of the hijackers.

Prosecutors in northern Virginia first gave strong signals they considered this a capital case when they wrote March 7 to dozens of victims' families to say that, pending Ashcroft's final approval, "the United States will be asking the jury to find that defendant Moussaoui should be executed should he be found guilty."

U.S. District Judge Leonie Brinkema already has denied a request by television networks to broadcast the Moussaoui trial, citing security concerns and a federal ban on cameras in federal courtrooms.