A one-time driver for Usama bin Laden helped the FBI try to track down his boss after being captured in Afghanistan, his former interrogators testified Wednesday.

Salim Hamdan led agents to the Al Qaeda chief's compounds in Kandahar and mapped out his movements among safehouses, training camps and other remote corners of Afghanistan in the month following the Sept. 11 attacks, FBI special agent Robert Fuller said at a pretrial hearing.

The U.S. military is now preparing to use the interrogations against Hamdan at the first American war-crimes trial since World War II. The Yemeni prisoner faces a maximum life sentence if convicted of conspiracy and supporting terrorism.

Hamdan's Pentagon-appointed attorney, Navy Lt. Cmdr. Brian Mizer, said the U.S. is not sufficiently taking into account the help that Hamdan provided following his capture.

"It's awfully suspicious for someone who is a hard-core Al Qaeda member as prosecutors claim," he told reporters.

One interrogator from the Naval Criminal Investigative Service, Michael St. Ours, said Hamdan acknowledged being close enough to bin Laden to know he was planning a major operation a week before the Sept. 11 attacks.

"He told that us after 9/11 took place, he asked bin Laden if that was the operation he was talking about, to which he said 'Yes,'" St. Ours said.

Hamdan, whose trial is scheduled to begin next week, was captured by Afghan forces at a roadblock in November 2001 and turned over to the U.S., which quickly realized his value in the hunt for bin Laden.

He drew maps identifying key locations including a guesthouse frequented by Al Qaeda members, according to testimony Wednesday. Hamdan's assistance continued after he arrived at Guantanamo in May 2002.

"I was trying to gain information from an individual who could help us," said St. Ours, who questioned Hamdan here three times the month he arrived in Cuba.

Prosecutors called Hamdan's interrogators to refute claims that he was coerced into making statements to be used against him at trial, and five agents said they never heard Hamdan raise allegations of abuse.

But a sixth, FBI agent George Crouch, said Hamdan told him he had been moved into solitary confinement during their sessions here in July 2002. Crouch said he protested to military commanders at the detention center, who moved him out of solitary, but he could not re-establish rapport.

"It really hurt what was going on and what we were trying to accomplish," Crouch said.

Also Wednesday, the military judge in the case denied a defense challenge arguing that the charges against Hamdan were not established as crimes at the time.

Defense lawyers had said the charges were therefore illegal under the Constitution, which the U.S. Supreme Court recently found has at least some applications to Guantanamo detainees.

The Bush administration set out to prosecute Guantanamo detainees nearly seven years ago, but the tribunals have been delayed by repeated legal setbacks. Hamdan is one of 20 inmates facing charges.

A U.S. federal judge in Washington has scheduled a hearing Thursday on whether to halt Hamdan's trial as he reviews whether the offshore prosecutions violate the Constitution.