President Obama will travel to Copenhagen, Denmark, to attend the start of an international conference on climate change, where he will propose cutting greenhouse gas emissions to levels matching House legislation awaiting Senate action.
At the summit, Obama will propose to cut greenhouse gas emissions by a range of 17 percent from 2005 levels by 2020, the White House said.
The 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.
For months, the White House delayed announcing a decision on whether Obama would attend the summit, a decision favored by liberal Democrats and climate change believers who note that the United States and China are the top two carbon emitters in the world.
But Congress has been stalled on climate change legislation as it battles over health care and the world economy tries to recover. Even with Obama in attendance, the world body is unlikely to reach a legally binding agreement at the summit. 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.
Obama's decision to attend drew mixed reactions divided along political lines.
"This could be one hell of a global game changer with big reverberations here at home," said Sen. John Kerry, D-Mass., a co-author of the Senate climate change legislation. "For the first time, an American administration has proposed an emissions reduction target and when President Obama lands in Copenhagen, it will emphasize that the United States is in it to win it."
But Sen. James Inhofe, R-Okla., the top Republican on the Senate Environment Committee, said the president's decision reeked of desperation, and pointed to the hacking of e-mails and documents from the Climate Research Institute in England as proof that global warming scientists are fudging their findings.
" I suspect President Obama is making the trip to Copenhagen in order to save the climate conference," said Inhofe, who is calling for an investigation into climate change research following the release of the documents. "Yet no amount of lofty rhetoric or promises of future commitments can save it."
"This is due in large part to the fact cap-and-trade legislation in the Senate is dying on the vine, and, as important, are recent revelations of leading climate scientists who appear to have manufactured the climate 'consensus' casting doubt over the entire global warming enterprise."
Rep. Henry Waxman, chairman of the Energy Committee and a co-author of the climate change legislation that narrowly passed in the House, called Obama's decision "a tremendously important step that changes the dynamic internationally and domestically."
"The president is providing the right leadership at just the right time," he said. "U.S. leadership has been the missing piece in international efforts to stop global warming. Now the rest of the pieces will start falling into place internationally and in Congress."
Yvo de Boer, U.N. climate treaty chief, joined the chorus of climate change activists when he told reporters in Bonn Wednesday that it is "critical" that Obama attend the summit.
"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."
The White House is sending a half dozen Cabinet officials as well, including Energy Secretary Steven Chu, Commerce Secretary Gary Locke, and Environmental Protection Agency chief Lisa Jackson. It is the highest profile contingent of U.S. officials to ever take part in international climate negotiations.
Obama said during his trip to Asia last week that the U.S. and China want the Copenhagen summit to lead to an agreement that has "immediate operational effect."
We "agreed to work toward a successful outcome in Copenhagen," Obama said after his meeting last week with Chinese President Hu Jintao.
Former Vice President Al Gore, who is delivering a lecture at the event, 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.
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 world leaders."
But other environmentalists said the visit will reinforce the U.S. government's shift on climate policy.
"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.
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.
Fox News' Mike Emanuel and The Associated Press contributed to this report.