"President Obama's commitment to dealing with global warming has changed the political dynamic for our negotiations," United Nations Secretary General Ban Ki-Moon told ABC News here at the Copenhagen Climate Summit.
"Everybody is looking to the U.S. for leadership and commitment in dealing with global warming," he said. "It has helped that he has repeated his commitment many times."
President Obama is expected to speak at the final plenary session of the conference after he arrives here early Friday.
Standing next to Ban was Achim Steiner, the Brazilian-born head of the United Nations Environment Program.
"Obama has improved humanity's efforts to fight climate change by bringing America back to the table," Steiner told ABC News, contrasting it to the attitude of the administration of President Bush.
Some speakers, including former Vice President Al Gore, have called on the U.N. to move up its next climate meeting from December 2010 to July, so that binding limits on greenhouse-gas emissions can be agreed upon more quickly. Steiner would not be specific about dates, but said speeding it up could have a good impact on world finance.
"Moving the date up would not only have a good effect on the climate," he said, "but also on markets."
"Hundreds of billions of dollars will be triggered or redirected once we have an agreement," Steiner said, adding his belief that "the world is immensely impatient" to make this transition to a carbon-restricted economy.
"Many of the world's markets and companies are waiting for a clear signal to tell if the world is going to move into a low-carbon era," he said.
The enormous meeting room was still filled with the many delegates and other attendees who had listened to an unusually intense and animated description by Secretary Ban of the climate issue and the "very difficult" negotiations to deal with it.
Many of the heads of United Nations organizatons -- the United Nations Development Program, the World Meteorological Organization, the World Food Program -- stood behind him as he spoke to the crowd.
"The U.N. has the widest and the deepest and the longest experience and know-how in helping people -- certainly in the developing world," he said, and affirmed that this entire "U.N. System", as it is called, has been working for two years on ways to provide aid to people as the apparently inevitable damages of global warming accelerate.
"We are user friendly!" said a smiling Ban to the capacity crowd.
Descriptions of human suffering that has already started worldwide as a result of human-induced global warming are heard throughout the day on the in-house monitors scattered throughout this vast convention complex.
One after another, delegates from poor and developing countries appear at a podium or microphone. They talk of the beginnings of mass migrations, long predicted by some scientists, of "climate refugees" looking for food or water. They describe the losses increasingly suffered from flood or drought that are now linked to worsening weather patterns produced by the rising average global temperature.
"For us, your disagreements are about our right to exist!" declared one man from one of the 37 "small island nations" at the summit.
His home island, he said, is expected to disappear under rising sea level in the coming decades.