Nader Khanmohammadi Ahmad Abad, 40, pleaded guilty on Friday to attempting to possess 10.83kg of pure opium, considered a marketable quantity, shipped from Turkey in January last year.

His barrister, James Fitzgerald, said Abad, who arrived in Australia by boat in 2013, had been taken advantage of by his co-accused.

"This stupidity has put him into a gravely parlous situation," Mr Fitzgerald told the County Court, while conceding his client faced a jail term.

Abad was arrested in suburban Burnside Heights on January 25, 2018, when the shipment was delivered by federal police who had switched the opium.

Prosecutors dismissed attempts to paint Abad's role as minor, saying his address was listed on the drug consignment and without him it could not have been delivered.

Abad is on a bridging visa and the court was told his status in Australia was "very much up in the air," with his safety at risk if he is returned to Iran.

Abad suffers post-traumatic stress disorder symptoms from his time in his home country and witnessed a "terrible situation" on the journey from Indonesia to Australia, his lawyer said.

At one point the asylum seeker spent up to six hours in the water.

Mr Fitzgerald described Abad as a hard worker of good character who had led an otherwise blameless life.

He saw his client making a "worthy" contribution to Australian society after his release.

Co-accused Saied Balager also travelled to Australia in 2013 by boat.

Balager is expected to stand trial over his alleged role in the opium importation, while Abad has been remanded in custody ahead of his sentence next Friday.

When police announced news of the bust they said 12.4kg of opium worth an estimated $16 million had been found in the base of an asphalt compacting machine.

Australian Associated Press