New Zealand's commitment to a new Commonwealth fund to help developing countries cope with climate change could be as high as $50 million annually.
However, Prime Minister John Key today said it was more likely to be about half of that.
Mr Key is attending the 53-nation Commonwealth leaders meeting in Trinidad and Tobago.
At the summit developed countries in the Commonwealth, led by Britain, backed an initiative to establish a Copenhagen Launch Fund, starting in 2010 and building to $10 billion annually by 2012.
The fund would help poor nations fight climate change and global warming.
"That would require New Zealand to make a contribution in the order of between $10 million and $50m so if you took a mid-point maybe it's $25m-$30m from New Zealand's point of view," Mr Key said on Radio New Zealand this morning.
Mr Key said funding for the global alliance on greenhouse gas emissions from agriculture, an initiative he announced earlier this year, could count towards New Zealand's contribution. The alliance aims to find ways to reduce harmful emissions from agriculture -- a big issue for many developing countries.
"I would envisage there would be additional resources that would have to go in to meet our obligations."
Nearly half of the Commonwealth's members are small island states, and developing nations have been appealing for hefty financial aid from rich governments to help them counter climate change and reduce carbon pollution.
The fund would go towards helping the poorest countries adapt to climate change with stronger sea and flood defences, tackling deforestation and building new, cleaner energy sources.
The summit also put its support behind Danish Prime Minister Lars Lokke Rasmussen's efforts to secure wide attendance and commitment from world leaders at the United Nations climate talks in Copenhagen next month.
Mr Key again stated that he did not plan to attend the talks but that could change if it became more likely a binding agreement would be reached. "If the position changes I am not opposed to getting on a plane."
The talks are not expected to result in the immediate approval of a detailed climate treaty but the Commonwealth climate declaration made clear its leaders expected any deal reached in Copenhagen would be "operationally binding" and lead quickly to a definitive treaty.
The deal the United Nations is aiming for in Copenhagen would cover tougher emissions targets, climate financing for poorer nations and transfer of clean-energy technology.
The climate treaty, expected to be adopted as a final text next year, will replace the Kyoto Protocol expiring in 2012.