Salim Ahmad Hamdan went before a panel of five US military officers for a pre-trial hearing at the US naval base in Guantanamo Bay where he had been held for more than two years without being charged.
On Tuesday he was charged with conspiracy to commit murder as a member of al-Qaida.
The US has charged four of the 585 alleged al-Qaida or Taliban suspects at Guantanamo with conspiracy to commit war crimes, a charge that carries a maximum penalty of life in prison.
Hamdan was the first to go before the controversial military tribunal authorised by US President George Bush for trying foreigners after the September 11 attacks in the US.
Human rights groups say the tribunals are totally biased because the US performs all the roles, from judge to jury. They also say there is no independent judicial review and that the rules are stacked to produce convictions.
The process is unfair because it applies only to non-US citizens, they add.
The US alleges Hamdan met bin Laden in Afghanistan in 1996 and became a personal driver and bodyguard for him and other high-ranking al-Qaida members.
With close-cropped black hair and a bushy moustache, Hamdan wore an ankle-length white robe and tan suit jacket for the hearing.
He was neither in handcuffs nor chains.
Hamdan's military-appointed lawyer, Lieutenant-Commander Charlie Swift, planned to ask that the charges be dropped on grounds the tribunal officers and rules had been improperly influenced by Bush administration officials.