Diplomats were preparing for one last push to find a compromise capable of bridging the divide between whaling nations and their opponents at the biennial International Whaling Commission summit in Slovenia.

A narrow majority of delegates have lined up behind a proposal from New Zealand to curb Japan's "scientific whaling" ambitions by enforcing strict oversight on the number of whales that it may cull, and the scientific justifications for this, particularly the availability of non-lethal means for conducting research.

As a voluntary body, the IWC cannot compel Japan to stop whaling, but stepping outside its aegis would be undesirable for Tokyo and frantic last-minute attempts are being made to find a consensus deal that could pass without a divisive vote.

"There may be a way of threading the needle," a key diplomatic source said, "but it will require some give on both sides and we have to find out whether people are prepared to do that. The trade-off is on the one hand, Japan accepting that the commission has a role to play, and on the other hand, a recognition that this isn't just a one-year deal. It is not all about 2015, but looking at the longer term."

No proposal, if it materialises at all, is expected until Thursday though.

Earlier this year, Japan suspended its "scientific whaling" programme for a year after the International Court of Justice ruled that it violated Article VIII of the IWC's whaling convention.

Japan has since declared an intent to resume scientific whaling in 2015 but the New Zealand resolution, if passed, would require that first the IWC's scientific committee and then the commission itself sign off on any new programme. Within the IWC's framework, this could normally only take place at the next summit in 2016, creating a de facto moratorium on the scientific whaling programme in the interim.

A retreat from this position would risk a backlash from the "Buenos Aires" group of Latin American nations, which favour a more robust environmental regime, particularly in the south Atlantic. It would also be unpopular with environmental NGOs, who are tenaciously clinging to the conservationist gains made at the IWC.

"We are totally against [weakening the original resolution]," said Aimee Leslie, WWF's global cetacean and marine turtle manager. "As a minimum we want the resolution to be accepted as is, and hopefully strengthened."

However, Gerard van Bohemen, the head of the New Zealand delegation, said a technical solution was possible, with goodwill from the two parties.

"Both sides would have to step back from their positions and come together around what should be a straightforward issue but has really become mixed up in the politics of scientific whaling," he said.

"It is about how you assess the scientific purpose of a scientific whaling programme, the size of a sample and whether that's reasonable in terms of the objectives you're trying to achieve, whether you've considered non-lethal options and whether they are a feasible way of achieving the same objectives."

Japan says that its past "scientific whaling" programmes have revealed that the age of sexual maturation for minke whales fell in the 1960s, but began to reverse in the 1990s, and that the thickness of blubber can serve as an indication of nutritional condition.

Some marine scientists question the relevance of cetacean's sexual maturation for their conservation and management, and whether the nutritional condition of whales could have been established without killing them.

Whale meat consumption is falling in Japan – as is the trade's profitability – but the issue remains a point of principle in Tokyo, according to van Bohemen,

"Japan is heavily reliant on marine resources for its food and I think that's why they've attached such high importance to it," he said. "Frankly, for the world's third-largest economy with so many other options, it seems like a unnecessary luxury and a burden."

One Japanese negotiator said that there were still wide differences between the two sides on the whaling question. "But I believe that we can try to find some common ground," he added.

Asked whether Japan would unilaterally resume scientific whaling if it lost the vote, he replied: "I do not reply to 'what if?' questions."