With just three days until the Copenhagen meeting begins, finance for measures to combat and adapt to climate change appears to be the biggest obstacle to securing a deal.

Denmark has invited heads of state and government of all UN member nations to the Copenhagen conference, and so far nearly 100 say they will attend.

Connie Hedegaard, Danish Climate Summit Minister, said, "I hope the world can agree on all the necessary elements, that being reduction, adaptation, technology and finance and I think it is very crucial that we actually deliver on all four elements."

China, India, Brazil and South Africa oppose setting a goal of halving world greenhouse gas emissions by 2050.

They insist that developed nations must make far deeper cuts in their own emissions by 2020. President Barack Obama plans to cut US emissions by three percent by then.

Connie Hedegaard, Danish Climate Summit Minister, said, "What the world is waiting for now is exactly what will be the American commitments to reduce their emissions."

Hedegaard said how much finance the US is prepared to commit is crucial together with fast-start financing for 2010-2012. She also said longer-term financing should include mechanisms to keep up a steady flow of money, such as levies on bunker fuels and aviation.