GUANTANAMO BAY NAVAL BASE, Cuba - A former driver for Osama Bin Laden says he never told a U.S. Defence Department agent that he swore an oath of loyalty to the terrorist leader.

Salim Hamdan told a judge at the Guantanamo Bay Naval Base that he never swore "bayat," contradicting the testimony of a former interrogator.

The judge presiding over the first Guantanamo war crimes trial is investigating whether the May 2003 interrogation is tainted by coercion and therefore inadmissible.

If the judge allows testimony that Hamdan swore "bayat," it would contradict defence lawyers' claim that he had no allegiance to al Qaeda.