A Virginia man accused of joining Al Qaeda (search) and plotting to assassinate President Bush admitted his guilt and pondered hijackings similar to the Sept. 11 attacks, an FBI agent testified Tuesday.

The testimony came at a pretrial hearing at which a federal magistrate said Ahmed Omar Abu Ali (search) posed a "grave danger" and ordered that he remain jailed pending trial.

Abu Ali, 23, was charged last week with providing support to Al Qaeda and conspiring to assassinate the president. Authorities allege that Abu Ali, who grew up in Virginia, joined Al Qaeda while studying in Saudi Arabia (search).

FBI agent Barry Cole testified that Abu Ali admitted many times that he joined Al Qaeda and discussed various potential acts, including a plan in which he would personally assassinate Bush.

Cole said other plans included hijacking planes in Great Britain and Australia and using them as missiles to attack targets in the United States, a plan to free prisoners at Guantanamo Bay and a plan to destroy naval ships in U.S. ports.

"The defendant has in his own words indicated he is a grave, grave danger to this community and this nation," Liam O'Grady said after hearing Cole's testimony.

Defense attorney John Zwerling said the various plots that Cole described were "preposterous."

"How is he going to free the brothers at Guantanamo? Is he going to take a rowboat? Doesn't that sound bizarre to you?" he asked Cole.

Zwerling claims the government obtained its confessions through torture, and that four attorneys had seen scars on Abu Ali's back that the defendant says were inflicted by Saudi authorities.

Zwerling said after the hearing that he has more evidence to confirm claims of torture, but he would not discuss specifics.

Abu Ali was in Saudi custody for nearly two years before charges were brought. Zwerling noted that the government had obtained Abu Ali's alleged confession in September 2003 and suggested that the government would have brought charges then if it had a strong case.

Instead, he said the government only brought charges in the face of a civil lawsuit filed by Abu Ali's parents that sought details of the U.S. government's role in his detention in Saudi Arabia.

O'Grady said he would reconsider his ruling in keeping the defendant in custody if the defense could offer more evidence about statements made last year by FBI Assistant Director Michael Mason. He told a Muslim audience in northern Virginia that he believed the government had no interest in prosecuting Abu Ali and that he might soon be released.

O'Grady called Mason's comments disturbing, and Zwerling said the comments are evidence that the government did not believe it had a case.

Cole testified that he interviewed Abu Ali over four days in September 2003. He said Abu Ali initially demanded a lawyer but changed his mind after agents told him that he could be prosecuted by Saudi authorities or held as an enemy combatant.

Cole, a counterterrorism agent, said Abu Ali's confessions are supported by the admissions of an Al Qaeda cell leader in Saudi Arabia who surrendered to authorities. Cole said the Al Qaeda cell leader gave Abu Ali money to purchase a laptop computer and cell phone.

Cole also testified that Abu Ali discussed with him plans to assassinate members of Congress. No further details were offered.

Cole said the Al Qaeda leaders gave Abu Ali two options: He could either become part of a martyr operation or he could establish a cell in the United States and he would "marry a Christian woman, assimilate into the community and he would be provided operatives."