At the end of a rancorous first day, the annual meeting of the International Whaling Commission (IWC) here has declared itself squarely for conservation.
The anti-whaling nations proclaimed a resounding victory, hailing a move away from the commission's traditional role of managing whaling.
Trying to keep order: The arguments at the meeting are bitter
They believe it will make all the world's whales safer.
But one whaling nation, Japan, said it might well leave the commission.
The decision came with a vote, agreed by 25 votes to 20, with one abstention, in favour of the so-called Berlin Initiative.
In practical terms, that will mean setting up an IWC conservation committee to tackle the many threats to cetaceans (whales, dolphins and porpoises).
These include climate change, pollution, entanglement in fishing nets, collisions with ships, humane killing methods, and habitat loss.
This is ridiculous, it's out of order. I'm resentful and I'm angry
Masayuki Komatsu, Japan's team leader
Crucially, the committee will address the problems of all cetaceans: until now the IWC, set up in 1946, has limited itself to the commercially valuable great whale species.
'Closing the door'
It has always had a dual role, conserving whales and managing whaling (which still continues, although the commercial hunt has been suspended since 1986).
Many countries have for years opposed any resumption of the killing, and have wanted the commission simply to help the whales to recover from the centuries of savage industrial whaling.
But the few remaining whaling countries have agreed the whales should be conserved only so that the hunt can one day resume.
They see the vote to accept the Berlin Initiative as a way of changing the commission's remit and closing the door to any future hunt.
"In this very sterile debate we've been having for years, the vote lays to rest the idea that the IWC is only about the resumption of commercial whaling," Andres Rozental, the commissioner from Mexico and one of the initiative's chief architects, told BBC News Online.
"It's a great day for those who want to save the whales, on a par with the day we agreed the whaling moratorium.
"It's a splendid afternoon, and I'm very pleased the world's whales can swim in peace for a little bit longer. I think today will go down to the glory of the IWC."
Ben Bradshaw, the UK Fisheries Minister, called the vote "very significant progress".
The International Fund for Animal Welfare said: "What was once a whalers' club has become a force for conservation."
'Nail in IWC's coffin'
But the leader of the Japanese delegation, Masayuki Komatsu, told BBC News Online: "This is ridiculous, it's out of order. I'm resentful and I'm angry."
"The whaling convention was created for the sustainable use of abundant resources. We know there are millions of whales out there, minkes, sei and sperm whales," Mr Komatsu said.
The anti-whaling lobby believes it has fundamentally changed the IWC
"This will prohibit access to resources one after the other. When this meeting ends Japan will seriously and deeply consider whether to leave the commission," he added.
Rune Frovik works for a Norwegian group that supports whaling, the High North Alliance.
He said: "This is one more nail in the IWC's coffin. It is simply drifting further and further away from its original objectives. We'll be encouraging the whaling nations - Norway, Japan and Iceland - to organise whaling outside the commission."
The three countries said after the vote they were reserving the right not to take part in or fund the initiative.