A quarter-century ban on commercial whaling — one of the world's most successful preservation agreements — could crumble altogether if conservationists cannot persuade Japan to cut back on the tradition it champions.

Delegates to next week's meeting of the International Whaling Commission (IWC) in Morocco will consider whether to allow limited commercial hunts if Tokyo stops pursuing whales in a southern sanctuary. Even adamant opponents are willing to sanction limited hunts on that condition, but it appears to be more than the Japanese are willing to concede.

"Japan holds the key, because Japan is the only country that is whaling in the Southern Ocean, the only country whaling in the sanctuary, the only country doing high-seas, long-distance whaling," said Susan Lieberman, director of international policy at the Pew Environment Group, which supports allowing some whaling.

At stake is the future of the IWC, the world's sole whaling regulator. After whaling devastated many species, the commission instituted a ban in 1986, but Japan, Norway and Iceland harvest animals annually under its various exceptions.

"The moratorium has been one of the single most effective conservation achievements of the century, but it's not working currently in the sense that several governments can whale completely outside the IWC's control," said Wendy Elliott, who will lead a group from WWF at the meeting.

The frigid Antarctic has become the focus of the heated debate. The area was declared a sanctuary in 1994, but Japan hunts there under a scientific exemption. Norway and Iceland conduct much smaller hunts near their own coasts, fuelling less anger from opponents.

Japan in conflicts over whaling

Each year in the Antarctic, Japan's whalers clash among the ice floes with militant anti-whaling group Sea Shepherd. Antarctic whaling has also boiled over into diplomatic channels.

Australia is taking Japan to the International Court of Justice, and the U.S. and a host of other countries have come out against the Antarctic hunts.

Japan maintains more scientific analysis is required in the region. It mostly catches Antarctic minke whales, aiming for about a thousand per year but often catching far less due to protesters.

Agreement within the IWC appears agonizingly close. Since a proposal was floated in April by the IWC chairman, some from the anti-whaling side, including the U.S. delegation, Greenpeace, the WWF and the Pew Group have said they would consider voting to allow limited hunts, and Japan has signalled it may accept taking fewer whales than it does now.

But in the days leading up to the conference that begins Monday, the sticking point remains the southern sanctuary. Any agreement will be voted on by the full 88 member countries, with the goal to reach complete consensus and eliminate all whaling under objections and exceptions.

With whalers and conservationists unable to bridge the gap over Antarctica, it appears another IWC meeting will pass without a deal.