Speaking to a town hall meeting of students at a university in the Philippine capital, Clinton said the Obama administration would push instead for a strong "framework agreement" that could become a template for an eventual enforceable pact.

"We are going to go to Copenhagen 100-percent committed to creating a framework agreement," she said. "We doubt that we can get to the legally binding agreement that everyone wants because too many countries have too many questions."

"But we do think that we can come up with a very strong framework agreement," Clinton told an audience at Manila's University of Santo Tomas.

Her comments echoed those she made earlier in the week at a meeting of Asia-Pacific foreign ministers in Singapore. That meeting precedes a weekend summit in Singapore of Pacific Rim leaders, including President Barack Obama, at which climate change will be a major topic.

"We cannot let the pursuit of perfection get in the way of progress," Clinton told a news conference on Wednesday, urging countries, many in Europe, that are insisting on forging a full-on treaty at the Dec. 7-18 Copenhagen talks to scale back their ambitions.

"If we all exert maximum effort and embrace the right blend of pragmatism and principle, I believe we can secure a strong outcome at Copenhagen and that would be a stepping stone toward full legal agreement," she said.

She added that the Obama administration remained committed to a "global legally binding climate agreement and will continue working vigorously with the international community towards that end."

But she stressed that "a final deal will not necessarily come quickly or easily."

At least 40 world leaders have said they plan to attend the Copenhagen conference, which follows two years of tough U.N.-led negotiations to draft a climate change agreement to replace the 1997 Kyoto Protocol, which expires in 2012.

They include British Prime Minister Gordon Brown, French President Nicolas Sarkozy and Dutch Prime Minister Jan Peter Balkenende. Obama has said he may come but has not yet committed.

The U.S., which shunned the Kyoto Protocol during former President George W. Bush's eight years in office, is seen as the linchpin to a deal. But it has been unable to present a position or pledge emission cut targets because of the slow pace of climate legislation in Congress.

Clinton said the framework agreement the U.S. seeks must have several elements: promises from all nations to do their fair share to reduce emissions, to transfer necessary technology, to commit to reduction targets or actions to that end, to ensure accountability with domestic pledges, and to assist developing nations with a global climate fund.

U.N. scientists say rich countries must cut carbon emissions by 25 percent to 40 percent from 1990 levels by 2020 to prevent Earth's temperatures from rising 2 degrees Celsius (4 degrees Fahrenheit) above its average temperature before the industrial era began 150 years ago. Any rise beyond that could trigger climate catastrophe, they say.

So far, reduction pledges total 11 percent to 15 percent, but those could be seen as negotiable.

The European Union - which has said it hopes to lead global climate policy - says it will meet or exceed its target of cutting greenhouse gas emissions by 8 percent below 1990 levels by the year 2012.

By 2020, the 27-member EU has vowed to slash emissions by 20 percent, and said it would step that up to 30 percent if the United States, China and other nations also pledge ambitious cuts in carbon dioxide emissions.

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