It did not call for a formal vote on the proposal when it became apparent it lacked the votes to get the measure passed.

The 77-member IWC voted earlier in the week to allow aboriginal whaling for indigenous people in the United States, Russia and Greenland. Japan endorsed those whaling quotas and had asked for the same consideration.

"This hypocrisy leads us to seriously question the nature by which Japan will continue participating in this forum," said Joji Morishita, the deputy whaling commissioner.

Opponents said Japan's proposal was a tacit request for permission to resume commercial whaling, 21 years after the IWC put a moratorium on the practice. Environmentalists credit the ban for saving the Earth's largest creatures from extinction.

Australian Environment Minister Malcolm Turnbull said passing the coastal whaling proposal would have set a precedent that could not be undone.

"The minute you open the door to commercial whaling, how do you shut it again? That is the problem," said Turnbull.

Japan said it was considering a number of options including leaving the IWC to start its own organization or resuming coastal whaling unilaterally.

Critics said this was a standard response from Japan.

"The only thing more familiar than their empty threat to leave the IWC is their disregard for decisions they don't like," said Patrick Ramage, head of the International Fund for Animal Welfare's global whale campaign.

Japan had postponed the vote on its proposal on Wednesday to allow more time for negotiation with anti-whaling nations, but the two sides failed to bridge their ideological divide.

Morishita suggested earlier in the week Japan was willing to give ground on a controversial plan to start hunting 50 humpback whales next year under its scientific whaling program in exchange for support for its coastal whaling proposal.

"HOSTAGE" HUMPBACKS

Japan -- which leads the pro-whaling bloc and has gathered support from African, Caribbean and some Asian nations -- is allowed to take more than 1,000 whales per year for scientific research. Critics say most of the meat ends up in supermarkets and restaurants and that Japan rarely publishes its findings.

Australia and its anti-whaling allies rejected a deal, saying Japan was attempting to hold humpback whales "hostage."

Humpback whales are noted for the complex songs sung by males and for their acrobatic behavior, making them popular with whale-watching tourists.

Their numbers have recovered somewhat and are estimated at between 30,000 and 60,000. This is still only about a third of pre-whaling levels and the species continues to be classified as vulnerable.

As a last-ditch effort, Japan offered a separate resolution asking the IWC's scientific committee for a method to calculate sustainable catch limits for its coastal villages so that the IWC could review quotas for Japan's coastal villages in 2008.

Japan requested its resolution be passed by consensus vote but decided against raising it for a formal vote after New Zealand and others expressed opposition.

Japan's threat to leave the IWC brought an end to a meeting that was, at times, both testy and conciliatory.

Earlier on Thursday, the IWC passed a proposal to let Greenland expand indigenous whale hunting after the Danish territory broke a deadlock by agreeing not to start catching humpback whales.

Greenland's representatives postponed the vote to negotiate and eventually agreed to give up a proposed new hunt quota of 10 humpback whales.