The information was contained in a Canadian intelligence service report that was partially released to a court on Thursday to justify the man's continued detention and eventual deportation. An earlier theory was that the bombing was carried out by Saudi dissidents opposed to the US presence in Saudi Arabia.
Nineteen US servicemen were killed in the attack which cast a shadow over relations between the US and Saudi Arabia, one of its main allies in the region.
According to the Canadian intelligence report, the man currently in detention - 28 year old Hani al-Sayegh - was responsible for gathering information about the building that was attacked, a military housing complex in Dharan, and for driving the car that signalled the go-ahead to the driver of the truck carrying explosives.
The report also said that Sayegh was a member of Hezbollah, the militant Shiite group commonly thought to be backed by Iran. Neither Canadian nor US officials would comment on the report, which was believed to be based on information gleaned at least in part by the US. The United States has made no secret of its interest in extraditing Sayegh.
Sayegh himself has denied any involvement in the Dharan bombing, saying that he was in Syria at the time. He says that he left Saudi Arabia because of political persecution and went to Canada to seek political asylum. He says the accusations against him have been trumped up by the Saudi authorities.