The New Zealand Government says a global deal on greenhouse gas emissions is unlikely to be signed at UN climate talks, but it has smaller goals it is confident it will reach.

Environment Minister Nick Smith said there was a greater chance of progress at the Cancun, Mexico, summit compared with the high-profile, but ultimately futile, Copenhagen meeting last year.

"I actually think it is helpful that there isn't the hype and high expectations of Copenhagen," said Dr Smith.

"If we are to get a comprehensive replacement for Kyoto beyond 2013, it will come from low-key, hard negotiation in which all parties do some giving."

He will travel to Cancun on Monday with Minister for International Climate Change Negotiations Tim Groser.

Cancun has lower ambitions than Copenhagen. Participants will try to agree on smaller packages such as a fund to channel aid to the poor, who are acutely affected by climate change, and ways to protect rainforests that soak up carbon.

One of Dr Smith's priorities will be achieving changes in the way forestry emissions are counted. Under current rules, trees are considered to give off carbon when they are harvested.

Dr Smith aims to have this changed so that wood products would be counted as carbon sinks (reservoirs which store carbon). This would reduce New Zealand's total emissions, and decrease the economic cost of buying credits from overseas.

Asked whether this goal was short-sighted, Dr Smith said preventing deforestation was the most cost-effective of all the initiatives to prevent dangerous climate change.

He said the rule change would provide a better incentive for developed countries to be able to grow their forestry industry and absorb CO2 from the atmosphere.

The Cancun summit will also attempt to heal the rifts between developed and developing nations around commitments to reduce emissions.

Tension remains from the Copenhagen meeting, in which nations bickered about which countries should bear the brunt of responsibility for curbing greenhouse gases.

The summit's executive secretary Christiana Figures has urged countries to find a compromise this year.

"When the stakes are high and the issues are challenges, compromise is an act of wisdom that can unite different positions in creative ways," she said.

New Zealand environmental groups similarly emphasised the need for our negotiators to be flexible.

Oxfam New Zealand executive director Barry Coates said if New Zealand focused too strongly on a forestry rule change it detracted from the greater vision of carbon reduction targets.

"It's a problem if you come into multilateral negotiations and sit there with your national hat on, saying, 'we'll do what's best for us as a country'. You're never going to get a good international agreement."

Mr Coates, who is in Cancun, said the international dynamic was changing at climate talks.

Developing nations such as Brazil and India were taking the lead due to their investment in renewable energies and a low carbon economy.

* Representatives from 194 countries are meeting to work on a binding resolution to reduce greenhouse gas emissions.

* These gases are widely believed to be the main cause of global warming and have been linked to predictions of flooding, sea level rises, droughts and heatwaves.

* It is the highest level talks since the Copenhagen Accord was signed last year, when leaders recognised the urgent need to prevent a global warming increase of 2C.

* An intergovernmental panel estimates that emissions will need to be reduced by 25-40 per cent to avoid that outcome.

* World leaders failed to make a global deal at Copenhagen, mostly due to disagreements between industrialised nations such as the US, and developing nations - China, India, Brazil.

* New Zealand set emissions targets at Copenhagen for 2020, but would only commit to them if it achieved rule changes in calculating emissions.