The UN's top court will rule Monday whether Japan has the right to hunt whales in the Antarctic, in an emotive case activists say is make-or-break for the giant mammal's future.
Australia in 2010 hauled Japan to the Hague-based International Court of Justice (ICJ), accusing Tokyo of exploiting a loophole by hunting whales as scientific research, despite a 1986 ban on commercial whaling.
Australia has asked the world court to order Japan to stop its JARPA II research programme and "revoke any authorisations, permits or licences" to hunt whales in the Southern Ocean.
During hearings last year, Australia accused Japan of doing nothing more than "cloaking commercial whaling in a labcoat of science".
While Norway and Iceland have commercial whaling programmes in spite of the 1986 International Whaling Commission (IWC) moratorium, Japan insists its programme is scientific, while admitting that the resulting meat ends up on plates back home.
Since 1988, Japan has slaughtered more than 10,000 whales under the programme, according to Canberra, allegedly putting the Asian nation in breach of international conventions and its obligation to preserve marine mammals and their environment.
In its application before the world court, Australia accused Japan of failing to "observe in good faith the zero catch limit in relation to the killing of whales".
Japanese officials declined to comment on specifics ahead of the ruling, but a Fisheries Agency official told AFP it maintained the view that "Japan's whaling is purely for the purposes of obtaining scientific data, so that whale resources can be sustainably maintained".
Tokyo has consistently defended the practice of eating whale meat as a culinary tradition.
Its lawyers have said the Japanese had a "proud tradition of living in harmony with nature, and utilising living resources while respecting sustainability".
Defiant Japanese Fisheries Minister Yoshimasa Hayashi last year vowed Japan would never stop whaling, a "long tradition and culture" in his country.
Japanese officials told AFP ahead of the ruling that Tokyo would accept the verdict from the ICJ, set up after World War II to rule in disputes between countries.
Australia also said it would respect the judgement but added that its views were clear: "We oppose all commercial whaling, including Japan's so-called 'scientific' whaling."
Japan in April last year announced its whaling haul from the Southern Ocean was at a record low because of "unforgivable sabotage" by activists from the militant environmental group Sea Shepherd.
Sea Shepherd, which called the ICJ case make-or-break for whales in the Southern Ocean, said it hoped for a decision that would ultimately protect the giants of the sea.
"We are still preparing to head down regardless (of the ICJ's decision)," said Jeff Hansen, director of Sea Shepherd, which spends about $4 million (2.9 million euros) annually on its anti-whaling campaigns in the southern oceans.
John Frizell of the environmental lobby group Greenpeace said a decision in favour of Australia "would place Japan in a very difficult position and present great difficulties for its operation in the Antarctic".
However, if the court rules in Japan's favour "they will feel vindicated and free to continue their operations, which are becoming increasingly controversial," he said.
Established in 1945, the ICJ is the UN's highest judicial body and the only one of five principal UN bodies not located in New York.