Japan says it has China's support in opposing a global ban on trade in Atlantic bluefin tuna.
Countries attending the Convention on International Trade in Endangered Species (CITES) meeting in Qatar this week will vote on whether or not to list blue fin tuna as endangered, and restrict its catches.
So far, fewer than 40 of about 150 countries attending have declared their intention to back a ban.
It would require a two-thirds majority of the countries present.
Japan consumes three quarters of the global catch of bluefin tuna, which is highly prized in sushi and sashimi and can fetch more than $US100,000 per fish.
Japan says it will ignore a ban, arguing bluefin is not facing extinction although it acknowledges that rates of exploitation are probably unsustainable.
The solution, it insists, is stricter management of fisheries.
Sea Shepherd off to CITES
Meanwhile, the anti whaling ship Steve Irwin is heading to the Mediterranean Sea to try to protect bluefin tuna.
Crew members say they want to raise awareness at the CITES meeting.
The Sea Shepherd Conservation Society's ship has recently been in the Southern Ocean targeting Japanese whalers.