Japan's opposition to extending the Kyoto protocol -- the binding international treaty that commits most of the world's developed countries to making emission cuts, is not very constructive, Brazilian Ambassador for Climate Change Sergio Serra said Wednesday.

Japan's stance on this issue "obviously will" be an obstacle to the Cancun Conference "unless Japan compromises a little bit," Serra told Xinhua in an exclusive interview. "There is no way to move forward if we don't have continuation of Kyoto Protocol". Japan's opposition was made by Jun Arima, an official in the government's economics trade and industry department. "Japan will not inscribe its target under the Kyoto protocol on any conditions or under any circumstances," he said late Tuesday in an open session.

It is the strongest statement yet made against the protocol by one of the largest emitters of greenhouse gases.

Serra said it's "ironic" that Japan, home country of the Kyoto Protocol, wants to throw it away.

Although the first commitment period of the Protocol will expire in 2012, Serra said, "the Kyoto Protocol itself has no expiration day."

The Kyoto protocol was adopted in Japan in 1992 by major emitting countries, who committed themselves to cutting emissions by an average 5.2 percent on 1990 figures by 2012.

However, the U.S. congress refused to ratify it and remains outside the protocol.

Serra also showed his suspicion about if the U.S. can fully honor its emission pledge.

"The U.S. is definitely not a positive partner," Serra said. " The U.S. negotiators have told us that they will stick to their commitment they made in Copenhage and they can do this regardless of a specific legislation on climate change and energy. They can do this through executive. I don't know if that is really possible. "

Serra thought that China, the biggest developing country in the world, is playing a "very constructive" role during international climate negotiations.

"China is working very hard in mitigation. China is carrying out very ambitious domestic programs in area of mitigation of cleaning up its coal plants and its reforestation is very ambitious," Serra said. "It's quite unfair to put the full responsibility for success or failure of this negotiations on China. China is not the only player (of the negotiations)."