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BONN, Germany — The Trump administration made its debut at a United Nations conference on climate change on Monday by giving a full-throated defense of fossil fuels and nuclear energy as answers to driving down global greenhouse gas emissions.

The forum — the only official appearance by the United States delegation during the annual two-week climate gathering of nearly 200 nations — illustrated how sharply the administration’s views are at odds with those of many key participants in the climate negotiations.

George D. Banks, special adviser to President Trump on international energy issues, led a panel with top American energy executives. “Without question, fossil fuels will continue to be used, and we would argue that it’s in the global interest to make sure when fossil fuels are used that they be as clean and efficient as possible,” Mr. Banks said. “This panel is controversial only if we chose to bury our heads in the sand.”