When this conference began more than a week ago, delegates were told that time is running out to do something to end climate change.
During these final days of negotiations, that message remains much the same, as Danish Prime Minister Lars Lokke Rasmussen reminded participants.
"I think the world is expecting us to reach some kind of agreement on climate change," he said.
Environment ministers joined their country delegations this week and negotiations have run through the night as heads of state and government have begun arriving.
But major differences remain and speeches often have contained the same rhetoric - North versus South, rich versus poor, who is to blame and who is the victim.
Remarks by Zimbabwe's President Robert Mugabe are a case in point.
"We are dealing with vested interests," he said. "We are dealing with dominant economies resting on a faulty eco-unfriendly development paradigm, aspiring to mis-rule the world."
But there also have been other approaches - an indication from African nations that they could scale back the amount of money they say they will need to cope with climate change. And there was a pledge from the United States of $1 billion to a $3.5-billion global fund to curb greenhouse gas emissions due to deforestation.
The U.N.'s top climate chief, Yvo de Boer, says there has been some progress.
"Significant amounts of money are being offered, targets have been tabled in a number of areas," he said. "On capacity building, on technology, on reducing emissions from deforestation, we've seen real advances on the substance."
But other key disagreements remain - including extending the 1997 Kyoto Protocol beyond its 2012 expiration date to cut greenhouse gases. Questions remain over who will cut emissions, by how much, how much it will cost and who will pay.
Doubts have been raised that this conference will achieve a binding agreement on climate change. And analysts say it might have to settle for a framework whose details will need to be filled in later.
But the U.N.'s Yvo de Boer remains optimistic. "I still believe that it's possible to reach a real success," he said. "But I must say, the next 24 hours are absolutely crucial."
More world leaders continue to arrive in Copenhagen to see whether differences can be ironed out for a climate agreement. U.S. President Barack Obama is expected to address the conference on Friday.