"We understand the gravity of the climate threat. We are determined to act," President Obama told a United Nations meeting on climate change in New York. "And we will meet our responsibility to future generations."
Tuesday's meeting at the U.N. General Assembly is designed to build momentum for the December talks in Copenhagen. U.N. Secretary General Ban Ki-moon said that negotiations are moving too slowly ahead of the critical meeting. Mr. Ban is the latest international official to raise concerns on the progress of negotiations. The gathering is set to establish a new agreement to limit the heat-trapping gases blamed for climate change when the Kyoto Protocol expires in 2012.
"U.N. negotiations need direct political support and guidance," Mr. Ban said.
Disagreements exist between developed countries, such as the U.S., and rapidly developing countries, such as China and India, over commitments to reduce heat-trapping greenhouse gas emissions. The flow of money from developed countries to developing countries to help cut emissions remains an issue as well.
President Obama sought to inject urgency into the negotiations, saying living standards and the health of the planet are at stake.
"The threat from climate change is serious, it is urgent, and it is growing," he said. "Our generation's response to this challenge will be judged by history, for if we fail to meet it -- boldly, swiftly, and together -- we risk consigning future generations to an irreversible catastrophe."
As some U.S. allies express skepticism over Congress's will to act, President Obama touted steps taken so far during his administration to cut carbon emissions and promote clean energy. He said more has been done in the last eight months than at any other time in history. But he acknowledged hurdles, particularly as countries focus on restoring economic growth.
"We seek sweeping but necessary change in the midst of a global recession, where every nation's most immediate priority is reviving their economy and putting their people back to work," Mr. Obama said. "And so all of us will face doubts and difficulties in our own capitals as we try to reach a lasting solution to the climate challenge."
Climate also will be on the agenda when Group of 20 leaders meet in Pittsburgh at the end of the week. President Obama said he would use that summit to phase out fossil fuel subsidies. The G-20 is expected to focus on how to finance the response to climate change. Agreements on funding flows from developed countries to developing nations are vital for a larger global climate change agreement.
President Obama said that the world's richest countries have a responsibility to provide financial and technical assistance to help emerging countries adapt to the impact of climate change. At the same time, he said developing nations responsible for most of the projected growth in global carbon emissions "must do their part."
"Some of these nations have already made great strides with the development and deployment of clean energy," President Obama said. "Still, they will need to commit to strong measures at home and agree to stand behind those commitments just as the developed nations must stand behind their own. We cannot meet this challenge unless all the largest emitters of greenhouse gas pollution act together. There is no other way."
In remarks at the summit, China's President Hu Jintao said his country will combat climate change in the next decade by reducing energy intensity even as the country grows, while increasing its reliance on renewable-electricity generation and nuclear power.
Mr. Hu said China would cut carbon per unit of gross domestic product by a "notable margin" by 2020, but didn't provide any exact figures. The rapidly growing nation also plans to get 15% of its power from renewable generation by 2020, while increasing forestry efforts.