Members of the Hamburg cell that led the Sept. 11, 2001, attacks wanted to fight alongside separatist rebels in Chechnya, but were told while in Afghanistan for training they were not needed in the southern Russian republic, a man charged with helping the hijackers told a court here today.

The statement by Mounir Motassadeq, a 28-year-old Moroccan who has acknowledged knowing the hijackers, buttresses the argument that the Sept. 11 plot originated with the leadership of Osama bin Laden's al Qaeda network.

The precise origins of the attacks have remained the source of speculation over the last year. Some Western officials have theorized that the leader of the hijacking group, Mohamed Atta, conceived the basic idea, but others have said it flowed from the top of al Qaeda. Motassadeq's testimony was consistent with the description of a chain of events in which the Hamburg group went to Afghanistan with one idea and returned with another.

In the opening day of his trial in a Hamburg state court, Motassadeq testified that he knew of Atta's ambition to fight in Chechnya and that the two men spoke together after Atta returned from Afghanistan in February 2000.

"Atta said to me, 'I was in Afghanistan and the people said to us that the Chechens do not need [fighters] anymore,' " Motassadeq testified.

Motassadeq has denied knowing anything of the Sept. 11 plot and said today that Atta, upon his return from Afghanistan, told him he wanted to leave Germany to obtain a doctorate in Malaysia.

"Atta was respected because of his behavior and not because of what he said," Motassadeq said. "He prayed regularly, and when he spoke, he was calm. He did not give off an aura of power."

The trial opened under heavy police guard in the city where the al Qaeda cell led by Atta operated undetected for 2 1/2 years before spearheading the attacks. Motassadeq is the first person anywhere to go on trial accused of direct involvement in the attacks; proceedings in a federal court in Virginia against an alleged al Qaeda operative, Zacarias Moussaoui, remain in the pretrial stages.

Motassadeq is facing more than 3,000 counts of accessory to murder, as well as being charged with membership in a terrorist organization. If convicted, he faces up to 15 years in prison.

The defendant "was aware of the objectives of the organization, aimed at the commissioning of terrorist attacks, and assisted in the planning and committing of those attacks by a great number of activities," the indictment states.

German prosecutors contend Motassadeq acted as the cell's banker. He forwarded money to hijacker Marwan Al-Shehhi in the United States and paid rent, utility and school bills for him in Germany to hide his activities, according to the indictment.

Hartmut Jacobi, one of Motassadeq's attorneys, complained to the court that the prosecutors had portrayed the case as a "terror trial" and said his client's activities were entirely unwitting. "We will ask the court to acquit him," Jacobi said. "We hope that the court will preside over a fair trial."

The trial could test the extent of U.S. cooperation in a foreign prosecution. Motassadeq's attorneys said in an interview this week that they want the court to call as a witness Ramzi Binalshibh, an alleged Hamburg cell member who was arrested in Pakistan last month and is being held by U.S. authorities at a secret location.

The defense hopes that Binalshibh will support the contention that Motassadeq assisted the hijackers out of brotherly courtesy because they were fellow Muslims, but was unaware of their plans. If U.S. officials do not permit his testimony, the attorneys said they will ask the panel of five judges to abandon the trial.

Under the German legal system, the lead judge will decide whether the court should hear from Binalshibh and whether his testimony must be taken in Hamburg or can be heard at another location, according to Felix Herzog, a professor of criminal law at Humboldt University in Berlin.

Because Binalshibh could face the death penalty after trial by a U.S. military tribunal, Herzog and other sources said, the United States is unlikely to return him to Germany, where he could launch court proceedings to prevent his return to U.S. custody. German law prevents handing over a suspect facing a possible death penalty.

While Motassadeq today denied the charges, he startled the packed courtroom by admitting he had traveled to Afghanistan in May 2000 for military training -- something that he, his family and his lawyers had denied for months. Motassadeq had maintained that he went only to Pakistan, for the purpose of visiting an Islamic country and studying his religion.

"This is nothing special," said Motassadeq's father, Ibrahim, of his son's stay in Afghanistan. Speaking from Marrakech in a telephone interview tonight, he added: "A lot of young Moroccan people have been there. He knew nothing about what happened in the United States. Everything he said today shows he is not guilty."

Under questioning today by the lead judge, Motassadeq said he went to Afghanistan after consulting with Atta. In his three weeks there, he said, he learned to use a Kalashnikov assault rifle and engaged in fitness training. He added that he believed the Koran compelled him to receive military training.

"I learned that bin Laden was responsible for the camp and had been at the camp sometimes," Motassadeq said. "I didn't know that beforehand, and I didn't meet him, either."

Motassadeq said he and Atta often discussed politics, including conflicts in the Palestinian territories and Chechnya, as well as U.S. foreign policy and the desirability of boycotting U.S. products. But he told Presiding Judge Albrecht Mentz that he never had any hint that Atta intended to commit acts of terrorism, adding, "In my opinion, it is no solution."

"Violence can never solve a problem. . . . You can't defend that as a Muslim," said Motassadeq, whose controlled delivery in German increasingly became agitated as the day progressed.

Special correspondent Souad Mekhennet contributed to this report.

Mounir Motassadeq, foreground, at opening of trial in Hamburg, is first person to be tried for direct involvement in Sept. 11 attacks.