The Danish chair of climate change talks in Copenhagen stepped up pressure on delegates to forge an effective deal as the conference entered its final stretch Thursday amid persistently deep divisions, DPA reported.
Danish media quoted Danish government sources as saying that the chair had "given up hope" of a successful deal being reached on Friday.
But sources familiar with the negotiations said such comments were aimed at turning up the heat on reluctant parties, especially members of the so-called G77 group of developing nations such as China.
The reports came in the wake of unsuccessful overnight attempts to get negotiations moving forward after a day of stalling.
But British Prime Minister Gordon Brown said in Copenhagen he remained confident that "by working together over the next 48 hours," the conference will be able to reach "a deal that will help the planet move forward for generations to come."
Sources close to the chair told the German Press Agency dpa that reports suggesting Danish Prime Minister Lars Lokke Andersen had given up hope were "untrue".
Others noted that Chinese Premier Wen Jiabao and United States President Barack Obama would not be travelling all the way to Copenhagen if a deal was not in the offing.
The only way to break the impasse is a backroom deal between the big players, especially the US and China, Norway's environment minister, Erik Solheim, told the Norwegian news agency NTB.
Thursday's talks were set to continue at both the informal and formal level, with a long-awaited Danish compromise text expected later in the day.
"It doesn't look good. We are still on procedural matters," a ranking member of the Swedish delegation told dpa earlier Thursday.
Sweden is the current holder of the rotating presidency of the 27- nation European Union, one of the negotiating blocs at the conference scheduled to end Friday.
The conference aims to slow global warming, but the nearly 200 participating nations remain at odds over the size of greenhouse gas emission cuts and the amount of financial aid needed by poor nations.
Meanwhile, Japan raised the prospects of a deal by increasing its climate funding commitment to developing nations to 15 billion dollars over the next three years.
Previous reports had suggested that Japan would be offering 10 billion dollars in "fast-start" money, a similar amount to that being offered by the EU.
With talks moving into the final phase, more heads of state and government were arriving in the Danish capital. In all 119 world leaders were due by Friday.