New Zealand's representative to the International Whaling Commission says the agency is in danger of breaking up.
Sir Geoffrey Palmer has been attending an informal IWC meeting in Florida, where New Zealand backed a compromise on whale hunting.
The proposal would allow Japan, Norway and Iceland to hunt whales, but reduce their total catch over the next 10 years. However, Australia rejects this.
Environment Minister Peter Garrett says Australia's primary objective is the total and permanent elimination of all whaling.
Sir Geoffrey says reaching a compromise is key, or the IWC is at risk of splintering.
He says conservation of whales would suffer if rival groups are formed.
Greenpeace says it's worrying that New Zealand has not backed Australia's bid to ban whaling.
The group's Oceans Campaigner, Karli Thomas, believes most New Zealanders would not support a compromise.
"If we reduce the number of whales that are hunted by a small amount now, but at the same time legitimise the return to commercial whaling, allow scientific whaling to continue and allow whaling to continue on an internationally-agreed whale sanctuary, we will actually set things back to last century in terms of what we're doing for the whales," she said.
"It will be a huge compromise."
The issue will be carried forward to the next formal meeting of the commission in Morocco in June.