The U.N. climate talks ran into serious problems Friday morning as negotiators tried to forge a political agreement for the summit meeting of President Barack Obama, China's premier and more than 110 other world leaders.

Delegates spoke of continuing disputes behind closed doors between developed and developing countries, the divide that has dogged the two-week U.N. climate conference from the beginning.

Swedish Environment Minister Andreas Carlgren said no agreed text had emerged just an hour before the presidents and premiers were to gather at a Copenhagen convention hall.

"It is now up to world leaders to decide," he said, suggesting they would have to make last-minute decisions on the thrust of the climate declaration. He blamed Chinese and U.S. positions for the morning's impasse.

Just before Obama landed in Copenhagen for the half-day of meetings and ceremony, a leading African delegate complained bitterly about the proposed declaration. "It's weak. There's nothing ambitious in this text," said Sudan's Lumumba Di-Aping.

Any agreement is expected, at best, to envision emissions-cutting targets for rich nations and billions in help for poor countries, but to fall well short of the goal of a legally binding pact.

The political deal would still be seen by many as a setback, following two years of intense negotiations to agree on deeper reductions in the emissions of carbon dioxide and other gases largely blamed for global warming.

The summit brings together the leaders of the two biggest polluting nations — Obama and Chinese Premier Wen Jiabao — and other heads of state or government for the signing of the declaration.

SLIDESHOW: Copenhagen Clashes

The U.S. and China had sought to give the negotiations a boost on Thursday with an announcement and a concession.

On the U.S. side, Secretary of State Hillary Rodham Clinton said Washington would contribute to a climate change fund amounting to $100 billion a year by 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.

Finding money to help poor nations cope with climate change and shift to clean energy seemed to be the issue where negotiators at the 193-nation conference could claim most success. The text under discussion early Friday included the $100-billion-a-year goal, to be achieved by 2020.

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.

Yvo de Boer, the U.N.'s top climate official, tried to put a more positive light on the discussions, saying a political deal could be the key to later unlocking the negotiating stalemate on a range of issues.

"Leaders came here to lead, and that's what they're doing. They're trying to reach an understanding on the key political components — and that's good," de Boer told The Associated Press well after midnight.

But he cautioned that a political declaration needed to include a deadline for agreeing on a replacement for the Kyoto Protocol, whose modest emission cuts for 37 industrialized nations expire in 2012. The U.S. rejects Kyoto and would be covered by a separate eventual agreement.

"You can reach an agreement here that sets out major political contours, a long-term goal, targets for industrialized countries, engagement by major developing countries, financing," de Boer said. "But people will want to see a clear deadline that turns that into a legally binding instrument."

Delegates filtering out of the predawn discussions over the final document sounded disappointed.

"It's a political statement, but it isn't a lot," said Chinese delegate Li Junhua.

"It would be a major disappointment. A political declaration would not guarantee our survival," said Selwin Hart, a delegate from Barbados speaking for the Alliance of Small Island States, many of which are threatened by seas rising form global warming.

The reality was that a political deal was about all leaders could expect from a process that has foundered the past two weeks over growing distrust between rich and poor nations. Both sides blamed the other for failing to take ambitions actions to tackle climate change and bickered over a post-Kyoto legal framework. At one point, African delegates staged a partial boycott of the talks.

World leaders handed off the draft text of about three pages at about 3 a.m. local time to their ministers and they continued to work on it through the night. But by 5 a.m., negotiators from Mexico and the G-77 plus China said they were nowhere near agreement on the final document.

Fernando Tudela, Mexico's vice minister of environment, agreed negotiators have their work cut out for them.

"There is still a possibility that something can be rescued at the last minute," Tudela said. "But otherwise it will be very difficult. There are still issues to be solved."

Clinton's announcement on funding was widely praised. Yoshiko Kijima, a senior Japanese negotiator, said it sent a strong signal by Obama "that he will persuade his own people that we need to show something to developing countries. I really respect that."

Swedish Environment Minister Andreas Carlgren said Clinton added "political momentum," and India's Environment Minister Jairam Ramesh called it "a good step forward."

But none of the leaders at the summit offered to increase their emissions targets, which the United Nations has concluded would fall far short of what is needed to avoid the worst impacts of climate change.

Sudan's Lumumba, spokesman for the developing-nations group, said the agreement that was being worked on included a goal of keeping temperatures from rising more than 2 degrees C above preindustrial levels, a ceiling a half-degree warmer than developing nations demand.

Carbon dioxide and other heat-trapping gases in the atmosphere have already increased global temperatures by 1.3 degrees F since the Industrial Age began the extensive burning of fossil fuels.

A U.N.-sponsored scientific panel says any further rise to above 3.6 degrees F more than preindustrial temperatures could lead to a catastrophic sea-level rise threatening islands and coastal cities, the die-off of many species of animals and plants, and damaging climate shifts to the agricultural economies of many countries.

An internal U.N. calculation, obtained by The Associated Press, said pledges made so far by both industrial and developing countries would mean a 4.8-degree Fahrenheit temperature rise over preindustrial levels.

Clinton repeated the U.S. would cut emissions by 17 percent from 2005 levels by 2020, and China said its voluntary emissions target was nonnegotiable. China announced last month it would cut its "carbon intensity," or the amount of emissions in relation to production, by 40 to 45 percent.

The European Union said Thursday that it will not raise its 20 percent cuts to 30 percent, as it has offered, unless it sees more ambitious actions from other countries, especially China.

The money announced by Clinton, to help poorer nations cope with climate change and develop clean-energy sources, was not guaranteed. The secretary of state said the U.S. agreement to an annual transfer of $100 billion in richer nations' public and private funds to developing countries was contingent on reaching a broader agreement that covers the "transparency" of China's measures to limit heat-trapping gases.

Chinese Vice Foreign Minister He Yafei told reporters Beijing had no legal obligation to verify its emissions actions, but was not afraid of supervision or responsibility.

"We will enhance and improve our national communication" to the U.N. on emissions, He said. The Chinese official indicated his country's emissions-cutting actions would then be open to international scrutiny, saying China was willing to provide explanations and clarifications on its reports.

"The purpose is to improve transparency," He said, adding that Beijing was ready to take part in "dialogue and cooperation that is not intrusive and doesn't infringe on China's sovereignty."