New Zealand's government said Friday that it would not sign on for a second stage of the Kyoto Protocol climate treaty, a stance that angered environmentalists and political opponents.

The announcement came the same day that Australia said it would stay the course and commit to "Kyoto 2."

The treaty aims to curb international greenhouse gas emissions through binding national reductions. But some question its effectiveness after many of the world's biggest polluters, including the United States and China, did not sign on.

New Zealand's climate change minister, Tim Groser, said he remained committed to emission reductions agreed to under the first Kyoto Protocol.

But Groser said the country would be better served in the future by joining the U.S., China and others in a nonbinding climate pledge under the United Nations Framework Convention. Those countries are working toward a new agreement that would take effect in 2020.

However, opponents said New Zealand's government was shirking its responsibilities and risking its international standing. Labour Party lawmaker Moana Mackey called it a "day of shame."

In announcing that his country would sign on for Kyoto 2, Australian climate change minister Greg Combet said in a statement that "Australia joins as countries around the world are taking action to combat climate change."

The Kyoto 2 treaty will run from 2013 to 2020.

Combet said it is vital that all countries make serious progress toward reaching the 2020 agreement, which would have legally binding reductions for all major polluting nations.