Mr Rudd defended Australia's actions
Australia has blocked three shipments to Iran because of fears the contents could have been for Tehran's nuclear programme, PM Kevin Rudd has said.
Mr Rudd told Australian radio Defence Minister John Faulkner had used powers under the Weapons of Mass Destruction Act to block the shipments.
But he declined to say when this happened or what the cargos were.
Mr Rudd defended Australia's actions, saying continuing strong international pressure on Tehran was essential.
"If you look at the threat to regional and global peace which Iran poses in its current nuclear weapons programme, there is no alternative other than robust international action including in areas such as this," Mr Rudd told public broadcaster ABC.
"We believe that national security, the national security interests of Australia, also demand this course of action," he added.
He said that Australia had acted "because we believe we must play the role of a responsible international citizen".
The Australian newspaper reported at least one of the banning orders, all made in recent months, had blocked a cargo of pumps that could have been used to cool nuclear power plants.
"If you look at the status of Iran's nuclear weapons programme and their consistent thumbing of the nose to the International Atomic Energy Agency, the international community more broadly... there are no alternatives other than to maintain a hard line," Mr Rudd said.
On Wednesday the United States circulated a discussion paper on possible further UN sanctions on Iran because of Tehran's nuclear programme.
This came as Iranian President Mahmoud Ahmadinejad apparently accepted a UN-brokered deal allowing Iran to send most of its low-enriched uranium abroad in return for research reactor fuel rods.
The US and its allies fear Iran is attempting to develop nuclear weapons. Iran insists its nuclear programme is entirely peaceful.