UN Secretary-General Ban Ki-moon and Danish hosts urged countries today to compromise to salvage agreement on a new UN pact aimed at averting dangerous climate change.
Ministers were struggling to break deadlock in global climate talks in Copenhagen, three days before world leaders were due to seal an accord.
"In these very hours we are balancing between success and failure," said Danish President of the two-week meeting, Connie Hedegaard, at the opening of the high-level phase of the talks.
"Success is within reach. But ... I must also warn you: We can fail."
Organisers of the talks said environment ministers would work deep into the night today to narrow wide differences, saying the bulk of the work must be complete before some 115 leaders formally join the meeting on Thursday.
"Three years of effort have come down to three days of action," Mr Ban said. "Let us not falter in the home stretch. No one will get everything they want in this negotiation."
President Robert Mugabe arrived in Denmark, despite Western sanctions on his travel and public disapproval from his Danish hosts.
Denmark's Prime Minister Lars Lokke Rasmussen said that Mr Mugabe was allowed to attend the Copenhagen climate conference because of rules that permit him to attend UN meetings, over-riding European Union and United States travel bans.
"That is the spirit of the UN - that the world needs a place where we can meet with those we basically don't like. And I guess that is how you can characterise the person you're asking about," Mr Rasmussen said when questioned about Mr Mugabe.
Mr Mugabe's arrival prompted local media to ask whether Danish leaders would shake the 85-year-old African leader's hand and whether, as elder statesman, Mr Mugabe will be seated next to Denmark's Queen Margrethe at a dinner on Thursday for heads of state and government attending the climate conference.
After a suspension of several hours the previous day, talks were stalled today over disputes about the level of emissions cuts by rich countries and a long-term global target to curb a rise in global temperatures which could trigger rising sea levels, floods and drought.
Draft texts dated today showed that national negotiators had stripped out figures for long-term global goals and rich nation emissions cuts by 2020 from last week's UN texts.
The numbers could be re-inserted if agreement is reached.
Major US businesses including Duke Energy, Microsoft and Dow Chemical called for tough US emissions cuts which would mobilise a shift to a greener economy.
"There's a great deal yet to do, the parties are quite far apart on a fair number of issues," said Todd Stern, US special envoy for climate change, adding he did not expect any change in US targets for emission curbs during the talks.
Ministers were expected to work late into the night. "It is not their (leaders') role to negotiate text," said Brazil's climate change ambassador Sergio Serra, emphasising that most work must be done by Thursday.
The Copenhagen talks, which Mr Ban described as among the most complex and ambitious ever to be undertaken by the world community, have stumbled over a long-running rich-poor rift on addressing the threat of climate change.
A "BASIC" group of China, India, Brazil and South Africa was "coordinating positions almost on an hourly basis", India's environment minister Jairam Ramesh said, reinforcing the entrenched rich-poor positions.
South African Environment Minister Buyelwa Sonjica, speaking for the group, said rich nation pledges for emissions cuts were "less than ambitious and ... inconsistent with the science." Developing nations also want the industrialised world to pay poorer countries to prepare for and slow climate change.
Japan would offer $10 billion in aid over three years to 2012 to help developing countries fight global warming, including steps to protect biodiversity, a Japanese newspaper said today. The European Union has offered a similar sum.
French President Nicolas Sarkozy said in Paris that he hoped US President Barack Obama supported "fast start" aid for developing countries. "President Obama often speaks about his links with Africa, it is time to show it," he said.
British energy and climate minister Ed Miliband, chair with Ghana of a group looking at the funding promises, said: "There are clearly still issues about the scale of public finance and what can be committed to at this point."
He pointed to wide divergence in positions. "The G77 (group of developing nations) wants 0.5 per cent of GDP - I don't think we're going to achieve that. The European Union has its figures, €22-€50 billion in 2020."
Reuters