Guantanamo Bay, Cuba: Osama Bin Laden's former driver said he felt "uncontrollable enthusiasm" when working for the Al Qaida leader and helped him elude capture, a US federal investigator said.

Salim Ahmed Hamdan, a Guantanamo detainee, said he drove Bin Laden and his son when they evacuated their compound near Afghanistan ahead of the September 11 attacks.

Robert McFadden, a Defense Department special agent who interviewed him, said Hamdan told him he had pledged an oath of allegiance to Bin Laden.

Hamdan said he heard Bin Laden say he had expected up to 1,500 deaths in the attacks but was pleased to learn there were many more.

The testimony was part of a pre-trial hearing to determine whether Hamdan is an unlawful enemy combatant who can be tried on war crimes charges in a US military tribunal.

Hamdan was captured on November 24, 2001, at a checkpoint near Kandahar while driving a car carrying two anti-aircraft rockets.