Updated at 11:57 a.m. Eastern.
A third draft climate agreement being considered by world leaders at the U.N. summit in Copenhagen has introduced greenhouse gas emissions targets for both industrialized and developing countries.
The document, titled the Copenhagen Accord, says rich countries should reduce their greenhouse emissions by at least 80 percent by the year 2050.
It says developing countries' emissions should be 15-30 percent below "business as usual," that is, judged against figures for energy used versus economic output.
The latest draft also reinstates a December 2010 deadline for when leaders should adopt a legally binding treaty on fighting global warming. An earlier draft dropped the deadline.
The news came as leaders, including President Barack Obama, held a second impromptu meeting in an effort to salvage a global climate accord.
In addition to Mr. Obama, the closed-door meeting included the leaders of Australia, the United Kingdom, France, Germany and Japan, according to White House spokesman Robert Gibbs. Also participating in the talks were developing countries Ethiopia, Bangladesh and Colombia, among others.
China and Russia, both seen as key participants in the U.N. sponsored climate talks, also were present, though Chinese Premier Wen Jiabao skipped the high-level meeting for a second time and sent another envoy instead.
The United Nations earlier had asked that the talks be extended into Saturday.
A White House spokesman said they're aware of the request, but said the "current plan is for [President Obama] to leave today," reports CBS News correspondent Peter Maer.
The Copenhagen summit has been enveloped in a diplomatic frenzy the final day, as a clearly frustrated President Obama displayed impatience with world leaders' failure to reach a new climate accord, urging them to accept a less-than-perfect pact while offering no new U.S. concessions.
Mr. Obama said the United States has acted boldly by vowing to reduce heat-trapping gasses and help other nations pay for similar efforts.
But he indirectly acknowledged that some countries feel the United States is not doing enough, and he said an imperfect accord is better than an impasse.
"No country will get everything that it wants," Mr. Obama said in a brief address to the 193 nations gathered here to cap a climate summit stalemated after two weeks of talks.
Without mentioning China specifically, he addressed Beijing's resistance to making its emissions-reduction pledges subject to international review.
"I don't know how you have an international agreement where we all are not sharing information and making sure we are meeting our commitments," Mr. Obama said. "That doesn't make sense. It would be a hollow victory."
Mr. Obama later held a private meeting with Jiabao as the two nations struggled to find common ground.
But neither leader offered any new commitments to cut the greenhouse gas emissions that cause global warming as they addressed the U.N. climate conference in Copenhagen.
"We are ready to get this done today but there has to be movement on all sides to recognize that is better for us to act rather than talk," Mr. Obama said, insisting on a transparent way to monitor each nation's pledges to cut greenhouse gas emissions.
Wen told delegates that China's voluntary targets of reducing its carbon intensity by 40 to 45 percent will require "tremendous efforts."
"We will honor our word with real action," Wen said.
After the private meeting, White House officials reported a "step forward" in negotiations in key issues including financing and transparency, reports Maer.
Meanwhile, other leaders were working on a potential deal with greenhouse gas emission cuts that could work, said U.N. Environment Program Director Achim Steiner.
Diplomats and leaders had only a handful of hours left for high-level talks to find the "miracle" answer that the Brazilian president said was needed for over 110 leaders to sign a deal at the conference's finale. Frustration and discouragement outweighed hope in the addresses by world leaders to the conference Friday.
"It's a rollercoaster of emotions," Steiner said. He told The AP the chance of a meaningful deal was now better than 50-50, but the talks were "in crisis mode" and weary negotiators could still scuttle an accord with one or two outbursts.
"(But) a deal is on the table, it is doable," Steiner said.
Many delegates had been looking toward China and the U.S. - the world's two largest carbon polluters - to deepen their pledges to cut the emissions of greenhouse gases that cause global warming. But that was not to be.
China has been criticized at the two-week offering stronger carbon emissions targets and for resisting international monitoring of its actions. After a morning meeting with 20 leaders, including Mr. Obama, French President Nicolas Sarkozy said progress in the climate talks was being held back by China.
"These two powers, very wary of each other, are each desperate not to have a deal here that will give strategic and economic advantage to the other," New York Times columnist Thomas Friedman told "Early Show" co-anchor Harry Smith Friday.
Friedman said the main sticking point for China was the U.S. demand for "transparency" - measures written into any agreement that would require Beijing to prove its actions to reduce emissions to the international community.
"The Chinese have basically said we promise not to go over the speed limit," quipped Friedman, "but we want no police, no courts, no stoplights, no real transparency on their carbon emissions… and President Obama is saying, 'If you think I can get that through the U.S. Congress - that China promises to be good on carbon, well, I've got a bridge in Brooklyn I'd like to sell you.'"
But the U.S. got its share of blame.
"President Obama was not very proactive. He didn't offer anything more," said delegate Thomas Negints, from Papua New Guinea. He said his country had hoped for "more on emissions, put more money on the table, take the lead."
Mr. Obama may eventually become known as "the man who killed Copenhagen," said Greenpeace U.S. Executive Director Phil Radford.
An early draft of the climate agreement, obtained by The Associated Press, called for rich countries to mobilize $30 billion over the next three years to help poor countries cope with the effects of global warming, scaling up to $100 billion a year by 2020.
But it called for continued negotiations on targets for emission cuts, with a deadline of a climate conference in Mexico City in December next year.
The lack of progress meant Mr. Obama changed the word "agreement" from his prepared speech to negotiators to "framework I just outlined."
United Nations Secretary General Ban Ki-Moon told climate negotiators that "the finishing line is in sight," reminding them that "the world is watching."
And Brazilian president Luiz Lula da Silva told negotiators how frustrated he was that the job was left to heads of state after the talks ran until just before dawn Friday.
"I am not sure if such an angel or wise man will come down to this plenary and put in our minds the intelligence that we lacked," Lula said. "I believe in God. I believe in miracles."
To move the talks forward, Lula said Brazil, a developing country, would give money to help other developing countries cope with the costs of global warming.
In a diatribe against the U.S., Venezuelan President Hugo Chavez criticized the climate conference as undemocratic.
"There is a document that has been moving around, all sorts of documents that have been moving around, there is a real lack of transparency here," he said. "We reject any document that Mr. Obama will slip under the door."
The conference has been plagued by growing distrust between rich and poor nations. Both sides blamed the other for failing to take ambitious actions to tackle climate change. At one point, African delegates staged a partial boycott of the talks.
"It is now up to world leaders to decide," said Swedish Environment Minister Andreas Carlgren.
Carlgren, negotiating on behalf of the 27-nation European Union, blamed the Friday morning impasse on the Chinese for "blocking again and again," and on the U.S. for coming too late with an improved offer, a long-range climate aid program announced Thursday by U.S. Secretary of State Hillary Rodham Clinton.
A leading African delegate complained bitterly about the proposed declaration.
"It's weak. There's nothing ambitious in this text," said Lumumba Di-Aping of Sudan, a leader of the developing nations bloc.
Any agreement was expected, at best, to envision emissions-cutting targets for rich nations and billions in climate aid for poor countries, butof a legally binding pact. If the political deal is done, it would still be seen by many as a setback, following two years of intense negotiations to agree on new emissions reductions and financial support for poorer nations.
China and the U.S had sought to give the negotiations a boost on Thursday with an announcement and a concession.
Clinton said Washington would press the world to come up with a climate aid fund amounting toby 2020, a move that was quickly followed by an offer from China to open its reporting on actions to reduce carbon emissions to international review.
That issue - money to help poor nations cope with climate change and shift to clean energy - seemed to be where negotiators at the 193-nation conference could claim most success.
Pollution cuts and the best way to monitor those actions remained unresolved. And negotiators also didn't come to an agreement on an important procedural issue - just what legal form a future deal would take.