Two years of UN climate talks reached their climax in Copenhagen on Friday without a deal on carbon emissions cuts, as world leaders tried a last push to agree a new global climate pact.

'There is still no text for the heads of state to negotiate,' a German negotiator told reporters after all-night talks. 'There are no results on anything. We have only several drafts. It's very, very difficult. Time is running out.'

At stake is a deal to avoid climate changes including more floods and droughts. The December 7-18 talks in the Danish capital have battled intense suspicion between rich and poor countries over how to share out carbon cuts that may drive up energy costs and will force a shift from fossil fuels.

'There are deep differences in opinion and views on how we should solve this. We'll try our best, until the last minutes of this conference,' said Swedish Prime Minister Fredrik Reinfeldt after overnight talks ended.

US President Barack Obama arrived on Friday morning, and would meet Chinese Premier Wen Jiabao on the sidelines, joining more than 120 other leaders in the largest ever climate summit.

Negotiators working through the night to prepare a text agreed an initial draft which called for a two degree Celsius cap on global temperatures and at least $100 billion in aid for poor nations, sources said.

But the all-night meeting broke up in the morning without a deal on the central element of a climate deal - the timing and degree of cuts in greenhouse gas emissions. 'It's still not there, it's confusing,' said a senior European negotiator.

'The situation is desperate,' said a top Indian negotiator emerging from the talks to agree a text that could form the basis of a political statement at the end of the Copenhagen negotiations.

'There is no agreement on even what to call the text - a declaration, a statement or whatever. They (rich nations) want to make it a politically binding document which we oppose.'

There appeared to be broad agreement on limiting the rise of global temperature below 2 degree Celsius from pre-industrial era levels, but not how to go about it.

Any final outcome could also include $30 billion in climate funds for least developed countries over and above a possible $100 billion a year funding by 2020.

Another developing nation negotiator told Reuters that rich nations were offering to cut their carbon emissions by 80 per cent by 2050, a proposal that had been rejected by developing nations. Developing nations have always insisted on the need for mid-term targets rather than long-term aspirations.

Another major issue is trying convince China and India, the world's top and fourth-largest carbon emitters, to allow outside scrutiny of pledged steps to curb their emissions.

The aim of the talks is to agree a climate deal which countries will convert into a full legally binding treaty next year, to succeed the Kyoto Protocol whose present round ends in 2012. The United States never ratified Kyoto, and the pact doesn't bind developing nations.-Reuters