COPENHAGEN, Dec. 17 (Xinhua) -- French President Nicolas Sarkozy required here on Thursday that the United States, as the most powerful country in the world, should provide more ambitious commitments, adding that all countries, industrialized countries in particular, should accept compromise.

    Addressing the high-level segment of the United Nations Climate Change Conference, Sarkozy said developed countries must "recognize that, when it comes to polluting the planet, their responsibility is heavier and more serious than for others, and so their commitments must be stronger."

    Meanwhile, German Chancellor Angela Merkel said: "I must say very honestly, that the United States' offer to cut emissions by 4percent compared to 1990 levels is not ambitious."

    The United States proposed to cut greenhouse gas emissions by 17 percent by 2020 compared with the 2005 levels. As for the climate change financing, the United States promised to join other rich countries in providing 100 billion U.S. dollars per annum by 2020 to help developing countries to deal with climate change, but set a condition that emerging economies should provide full transparency of the implementation of their mitigation actions.

    German Chancellor Merkel noted that the U.S. offer was "unambitious" and the pledges made by industrialized nations were also "not sufficient."

    Speaking at the conference, British Prime Minister Gordon Brown called on all developed countries to raise to the highest possible level their ambition for 2020.

    At the two-week conference, some developed countries have tried to abandon the Kyoto Protocol. Developing countries insisted that the talks should be conducted under two tracks, the Convention and the Kyoto Protocol.

    Sarkozy backed the calls by developing nations to keep the Kyoto Protocol. "A failure in Copenhagen would be a catastrophe for each and everyone of us," he said.

    Brown also stressed that the principle of "common but differentiated responsibilities" should be recognized.

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