New Zealand will join the Copenhagen Accord on climate change, with the same targets it took to the meeting there in December, Prime Minister John Key announced yesterday.

Copenhagen ended with what was regarded as a weak agreement among only a subset of the countries attending that they would plan to limit the increase in global mean temperatures to 2C.

The accord is a political agreement which, unlike the Kyoto Protocol, has no legal standing under the United Nations Framework Convention on Climate Change.

Countries wishing to associate themselves with it had until last Sunday to submit their emissions reduction targets, in the case of developing countries, or what they will do to curb growth in emissions, in the case of developing ones. Most, including the United States, the EU and Australia, have reiterated offers they took to Denmark.

New Zealand's offer, set by the Government last year, is to cut emissions by 10 to 20 per cent from 1990 levels by 2020.

But that is subject to a series of conditions, one of which is that there is a global agreement that sets the world on a pathway to limit a global temperature rise to no more than 2C.

The offers on the table from major emitter nations fall well short of that.

"It is the Government's view that for us to commit to a binding treaty in the 10 to 20 per cent range other significant emitter nations would have to increase their commitments in the negotiations ahead," Climate Change Issues Minister Nick Smith said.

"If there is no shift in the positions it is New Zealand's view that the conditions we have set will not have been met and we would need to set a target of less than 10 per cent."

The Government also wants changes to the Kyoto Protocol rules relating to forestry and to ensure there is no restriction on New Zealand's ability to meet its obligations by importing "carbon" - traded units representing a reduction in emissions somewhere else in the world.

Some countries want to limit using international carbon markets, seeing them as a disincentive to reduce emissions through domestic action.

The rules say that when a forest is felled, unless that land is replanted, all the carbon stored in those trees is deemed to be emitted to the atmosphere and has to be counted.

New Zealand says it ought not to matter whether the same land is replanted, only that a forest is grown somewhere.

It is uncertain in what forum climate talks are likely to make progress.