Japan dealt an early blow to hopes for extending a treaty that commits most of the world's richest countries to cutting greenhouse gas emissions.

The island nation surprised the Cancun climate summit with a statement opposing continuation of the existing deal, known as the Kyoto protocol, which expires at the end of 2012.

In the face of opposition to a new deal from United States and China, some Cancun negotiators had hoped for a defacto agreement to continue the Kyoto protocol, under which 16 major nations committed themselves to cut emissions by an average 5 per cent below 1990 figures by 2012.

The US refused to ratify the Kyoto accord. Canada signed the deal but made no effort to keep its commitment.

Japan's brief statement, made in an open session on Tuesday evening, was the strongest yet made against continuing the Kyoto protocol by one of the largest emitters of greenhouse gases.

"Japan will not inscribe its target under the Kyoto protocol on any conditions or under any circumstances," Jun Arima, an official in the government's economics trade and industry department, told the conference.

Japan gave no explanation for making its statement on the second day of the talks.

The statement provoked concern among the "G77" developing nations who regard the Kyoto protocol as the world's only binding agreement on climate change.

Monte Paulsen reports on carbon shift for The Tyee.