The interruption came after the FBI returned seized evidence to Afghan authorities.
Judge Abd Al-Basit Bahktiari adjourned the trial for a week on 16 August to allow the Americans - said to be bounty hunters - and their four Afghans co-accused time to study the evidence, which prosecutors said had been held by the FBI for more than 20 days.
The defendants, appearing on Monday, were arrested in July for allegedly running a private prison and counter-terrorism operations in Kabul. They had earlier accused the FBI of withholding evidence proving their links to US authorities.
Jonathan Keith Idema, Brent Bennet and Edward Caraballo along with their Afghan partners, face jail sentences of between 16 and 20 years if found guilty.
Idema says the group was working with the full knowledge of US Defence Secretary Donald Rumsfeld to hunt down terrorist suspects and had foiled bomb plots to assassinate senior government leaders and US troops.
Both the US and Afghan governments have disavowed any ties with his outfit.
However, Idema did have contact with both the US military and multinational peacekeepers in Afghanistan prior to his arrest.
Since he was arrested in early July, NATO-led peacekeepers have admitted they provided Idema's group with bomb disposal services, while the US military said they took a detainee arrested by Idema into custody.
NATO-led peacekeepers have
admitted ties to the group
The man was released by US troops after a month when they found he was not the wanted person Idema had said he was.
Both NATO-led peacekeepers and US forces said they were duped into helping Idema, believing him to be a legitimate special forces operative because of the way he behaved and the US-style military uniform he wore.
The case has shone a spotlight on the shadowy world of security and counter-terrorism in a country where US-led forces and international peacekeepers stay close to their bases, leaving a wide swathe for private security contractors to operate.
Lack of transparency
Earlier this week a UN official working on human rights in Afghanistan called on US officials to open their detention facilities to independent inspection.
Afghan human rights groups said Idema's case had highlighted the lack of transparency surrounding the jailing and detention of suspected fighters.
Idema, who has spent time in Afghanistan since 2001, claims ties with Northern Alliance forces who threw the hardline Taliban regime from power and denies reports he was a bounty hunter.
The former US army soldier spent three years in jail in the 1980s for fraud charges.