By Alex Kirby
BBC News Online environment correspondent, in Sorrento
Japan has set 2006 as a deadline to leave the International Whaling Commission if it is still unhappy with the organisation's performance.
The IWC is holding its annual meeting in Italy
A senior member of its delegation at the IWC annual meeting told BBC News Online it could not wait much longer.
This marks the first time Japan has set a date to implement its annual threats to withdraw from the IWC.
Japan heads the pro-whaling faction, still a minority on the commission but growing steadily.
Mr Yoshimasa Hayashi, a member of parliament for the ruling Liberal Democratic party, chaired a group it set up to discuss Japan's place in the IWC.
The group's members said earlier this year they were prepared to leave the "totally dysfunctional" IWC and establish a new pro-whaling alliance.
Mr Hayashi told BBC News Online: "My constituents ask me why Japan remains a member of the commission. It promised that by 1990 it would review the moratorium on commercial whaling which came into effect in 1986, but it's done nothing.
"Last year, without consulting us, it agreed to establish a conservation committee, which we oppose as a distortion of the IWC's fundamental purpose. I told officials in the White House that if we see no clear sign of improvement, we'll have to take the walk-out option seriously.
"This year's meeting, and next year's in South Korea, are the important ones. The Japanese people can't wait any longer than two more years.
"We might not set up a new whaling alliance: we might decide to play a more active role in the North Atlantic Marine Mammal Commission (Nammco)."
Japan sees whaling as an important part of its culture
It is not clear whether Nammco would be recognised under international law as competent to replace the IWC.
The Sorrento meeting may see the IWC's dwindling anti-whaling majority finally overturned. But even if the whaling countries - led by Japan, Norway and Iceland - secure a simple majority, that will be of greater political than practical importance, as a decision to end the moratorium needs a 75% vote in favour.
Mr Hayashi told BBC News Online: "If we do get a simple majority here, that would be a very good sign. It would let us either abolish the conservation committee, or change it to embrace both conservation and the sustainable use of whales."
He said the opponents of whaling regarded whales as pets. Mr Hayashi said: "They know many whale stocks are abundant. In Japan we have pet dogs. But we don't tell the Koreans to stop eating dogs. Nor should people tell us to stop eating whales."
In his opening statement to the meeting the leader of Japan's delegation, Mr Minoru Morimoto, said the public and parliamentarians had "come to the end of their patience".
Japan kills minke, sei, Bryde's and sperm whales for what it says is scientific research.
Mr Morimoto said it would continue its Antarctic whaling and increase its catches in the North Pacific.
Norway says it plans to increase its annual catch of 6-700 North Atlantic minke whales, possibly to 1,800 animals, by 2008. Because it objected to the moratorium when it was agreed, Norway is not bound by it.
Conservation groups here say Japan will achieve a majority on the IWC only by buying the votes of small nations, a charge Japan rejects.
Asked for evidence to support the claim, Fred O'Regan, president of the International Fund for Animal Welfare, told BBC News Online: "Look at the voting records. If it looks like a duck, walks like a duck and says it's a duck, then to me it's a duck.
"We're not opposed to Japan: we just hope it will see the light."