The United States, Japan and Australia are working together on ways to make it easier to stop North Korean ships suspected of carrying drugs and missile parts.
Japan is already stepping up surveillance of North Korean vessels
Australian Foreign Minister Alexander Downer said officials from the three countries would discuss the possibility of seeking changes to international law so that North Korean vessels could be stopped on the high seas.
The issue follows the seizure in April by Australian authorities of a North Korean boat, the Pong Su, found to be carrying 50 kg of heroin.
The US has long complained about North Korea's selling of missile technology around the world, and last year detained a ship carrying Scud missiles to Yemen.
Some members of the US administration have also argued that stopping illegal North Korean trade would deprive the impoverished state of a major source of income and hasten the regime's collapse.
'Act of war'
Mr Downer was speaking a day after Japan detained two North Korean cargo ships in Japanese ports for safety checks.
An Australian diplomat, Ashton Calvert, is due to meet officials in Tokyo on Wednesday to discuss the proposals. He is also due to meet US Deputy Secretary of State Richard Armitage, who is also visiting Tokyo.
Mr Downer stressed that the three countries were not discussing a blockade on North Korean ships.
Pyongyang has warned that it would consider economic sanctions as an act of war.
"First of all you have to get the countries through whose territorial waters ships might pass or across whose land planes may
fly or whatever to do the interdiction themselves within their own sovereign territory," Mr Downer told ABC radio.
"Secondly you are confronted with a very real difficulty in terms of vessels that might be going through the high seas because international law requires that those ships should not be intercepted," he added.
Mr Downer noted there was "good international support" for discussion of changes to international maritime law, but stressed the need to include China in future talks.
China is North Korea's closest ally and has been reluctant to support US policy towards North Korea.
Mr Downer said a conference in Madrid on Thursday would examine in greater
detail how to counter illicit and nuclear trade.
One boat that has been at the centre of suspicions about North Korean contraband is the Mangyongbong-92 - the only passenger ferry between Japan and North Korea.
North Korea suspended the service this week after Japanese authorities planned to search its cargo.
The North Korean official KCNA news agency said on Wednesday that the move was a "ridiculous plot... to suspend the ship under any pretext."
It warned of the "serious consequences" if this meant the start of sanctions against North Korea.
Mr Armitage is visiting Tokyo as part of US efforts to discuss with its regional allies Japan and South Korea how to handle the stand-off over North Korea's nuclear ambitions.
Japanese media quoted US officials as saying they were hopeful North Korea would take part in a new round of talks within the next month or two. The talks were likely to include South Korea, Japan and China.