Obama was speaking after talks with Chinese President Hu Jintao in which he said the world's top two greenhouse gas emitters had agreed to take "significant" action to mitigate their output of carbon dioxide.
"Our aim (in Copenhagen) ... is not a partial accord or a political declaration but rather an accord that covers all of the issues in the negotiations and one that has immediate operational effect," Obama said.
Denmark, host of the Dec. 7-18 climate talks, welcomed Obama's comments and said it expected the United States and all developed nations to promise firm emissions cuts and new cash to help the poor cope with global warming, even if no treaty text could be agreed , Reuters reports.
Meanwhile, together the United States and China account for 40 percent of world emissions, so their support is vital to any agreement.
"Our aim there ... is not a partial accord or a political declaration but rather an accord that covers all of the issues in the negotiations and one that has immediate operational effect," Obama said of the Copenhagen talks.
The international community had set a December deadline to agree a framework to tackle global warming from 2013, but a rift has opened between developed and developing nations over who should cut emissions, by how much, and who should pay for it.
Danish Prime Minister Lars Lokke Rasmussen, in a last-ditch bid to dispel growing gloom about the talks he will host from December 7-18, has proposed a delay in a legally binding pact until 2010 or later and aim for a political deal first, Reuters reports.
News agencies also report, talks in Beijing produced pledges of cooperation on climate change, the economy and even military relations but yielded no breakthroughs on the many global headaches that Washington wants Beijing to help relieve.
A stiff joint appearance by Obama and Hu in the Great Hall of the People overlooking Tiananmen Square crystallized the state of the relationship between the two world powers: increasingly important to both countries, but also curiously bereft of warmth or intimacy.
Hu, speaking first, said that as the world economy "has shown some positive signs of stabilizing and recovering," it is important for both countries to "oppose and reject protectionism in all its forms."
Obama called climate change and nuclear proliferation "challenges that neither of our nations can solve by acting alone." He said the two will continue to "build a positive, cooperative and comprehensive relationship , " The Washington Post reports.