World leaders tried to inject momentum into climate change talks yesterday but new proposals by China and a rallying cry from US President Barack Obama did little to break a United Nations deadlock.
Mr Obama and Chinese President Hu Jintao, leaders of the world's top greenhouse gas polluters, had hoped to help foster efforts to forge a new global warming treaty two and a half months before a December deadline.
Speaking at a special UN climate change summit in New York, Mr Hu laid out a new plan to tackle China's emissions but failed to include specific figures.
Mr Obama outlined his administration's efforts since he took office in January but offered no new proposals.
Mr Hu said China would vigorously develop renewable and nuclear energy and promised emissions would grow slower than economic growth in the future.
"We will endeavour to cut carbon dioxide emissions per unit of GDP by a notable margin by 2020 from the 2005 level," Mr Hu said, according to a prepared text of his remarks.
The pledge, while short of an absolute cap on output, was seen as an attempt to counter critics, especially in Washington, who say Beijing is doing too little.
Mr Obama said the US had done more over the eight months of his presidency to reduce carbon pollution than at any time in history and urged all nations to act together.
"Our generation's response to this challenge will be judged by history, for if we fail to meet it - boldly, swiftly, and together - we risk consigning future generations to an irreversible catastrophe," Mr Obama said.
"The time we have to reverse this tide is running out."
Activists and analysts expected more.
"It was a bit disappointing that China did not give a number for greenhouse gas intensity. I had expected it to come now," said Knut Alfsen, head of research at the Centre for International Climate and Energy Research in Oslo.
"But this is progress. Five years ago climate was a non-issue for China. Now they have turned around and are saying 'we are going to do something now.' This is a tremendous shift."
Environmentalists assailed Mr Obama for having few specifics in his first presidential speech to the UN.
"We are really very, very disappointed about what Obama has said," said Thomas Henningsen, climate coordinator for Greenpeace International.
"It is really more of a step back than a step forward," he said, adding that Obama had not spelled out any concrete steps compared to what Japan and other nations were prepared to do.
Europeans, who had welcomed Mr Obama's commitment to fight climate change as a positive development after his predecessor George W. Bush, have grown impatient.
A climate change bill mandating cuts in US emissions is unlikely to be passed by the US Senate by December while other domestic issues, notably healthcare reform, dominate the congressional agenda.
French President Nicolas Sar-kozy proposed that heads of state from major economies meet in November ahead of the Copenhagen talks.
UN Secretary-General Ban Ki-moon, who called yesterday's meeting, said talks were moving too slowly.
"Failure to reach broad agreement in Copenhagen would be morally inexcusable, economically short-sighted and politically unwise," Mr Ban said.