The president will take part in the conference Dec. 9 before heading to Oslo to accept the Nobel Peace Prize. The White House announcement Wednesday ended heavy speculation about whether Obama would attend the summit amid expectations that it likely will not produce a binding climate agreement.
The White House called Obama's decision "a sign of his continuing commitment and leadership to find a global solution to the global threat of climate change."
The president will lay out his goals for reducing the United States' carbon dioxide emissions by about 17 percent from 2005 levels by 2020. That target reflects climate legislation still pending on Capitol Hill. A House-passed bill would slash heat-trapping pollution by 17 percent. A Senate bill seeks a 20 percent reduction, but that number is likely to come down to win the votes of moderate Democrats.
Obama's commitment to that goal would reverse long-standing U.S. opposition to mandatory emission cuts during eight years of the Bush administration.
The White House also said a half dozen Cabinet officials including Energy Secretary Steven Chu and Commerce Secretary Gary Locke as well as the head of the Environmental Protection Agency - which is preparing regulations to cut greenhouse gases - will take part in the Copenhagen talks. It is the highest profile contingent of U.S. officials to ever take part in international climate negotiations.
The conference had originally been intended to produce a new global climate change treaty on limiting emissions of greenhouse gases that would replace the 1997 Kyoto Protocol. However, hopes for a legally binding agreement have dimmed, with leaders saying the summit is more likely to produce a template for future action to cut emissions blamed for global warming.
At least 75 world leaders will attend. Unlike Obama, most are expected to attend the final days of the Dec. 7-18 conference.
Danish Prime Minister Lars Loekke Rasmussen, the host and chairman of the talks, said of Obama's decision to attend: "The visit underlines the president's desire to contribute to an ambitious, global agreement in Copenhagen."
Yvo de Boer, U.N. climate treaty chief, told reporters in Bonn Wednesday that Obama's attendance was critical. He said, "The world is very much looking to the United States to come forward with an emission reduction target and contribute to financial support to help developing countries."
While Obama tried to tamp down expectations during his trip to Asia this month, he also called on world leaders to come to an agreement that would have "immediate operational effect" and not be just a political declaration.
Former Vice President Al Gore had urged Obama to make the trip. Gore's participation in the 1997 Kyoto talks were key to breaking an impasse that threatened the climate talks that eventually produced an agreement by developing countries to cut greenhouse emissions. The United States, however, never ratified the agreement and the Bush administration walked away from it.
While Gore flew to Kyoto as intense discussions were under way, Obama's visit to Copenhagen will be at the beginning of the talks when the conference agenda will be largely ceremonial.
"The Copenhagen climate summit is not about a photo opportunity," said Kyle Ash, climate policy adviser for Greenpeace USA. "It's about getting a global agreement to stop climate chaos. President Obama needs to be there at the same time as all the other wold leaders."
But other environmentalists said the visit will reinforce the U.S. government's shift on climate policy from that of the Bush administration, which rejected the 1997 Kyoto climate accords out of hand and over eight years steadfastly opposed broad mandatory reductions in greenhouse gases.
"It's a clear signal to the world that we're serious ... that he is committed to this issue," said Jake Schmidt, international climate director for the Natural Resources Defense Council. Schmidt cautioned not to expect Obama to "bring back the final deal" on climate, but he said it would help to establish momentum for an agreement next year.
The United States hopes to counter complaints by some delegates in Copenhagen that the U.S. has yet to establish mandatory emission reductions and that - despite Obama's speeches - it may not anytime soon, given the partisan fight in Congress over legislation to require economy-wide reductions in heat-trapping pollution. Congressional Republicans, as well as some centrist Democrats, have opposed the climate legislation, arguing it will result in higher energy costs at a time of economic problems.
In a statement announcing Obama's trip, the White House listed areas where the administration has taken a variety of steps both domestically and internationally to reduce America's reliance on fossil fuels - from the $80 billion in spending on clean energy as part of the economic recovery package to a requirement for significant increases in auto fuel economy by 2016, and agreements with China and other nations to promote energy efficiency and clean energy development.
Associated Press Writer Jan Olsen in Copenhagen contributed to this story.