Cambodian Prime Minister Hun Sen on Monday urged rich countries to take more responsibility for causing climate change, saying poorer nations were the ones to suffer the fall-out.

"All of us poor countries do not cause climate change. (We) would like rich countries to take a bit more responsibility than before," Hun Sen said, branding it a "sin".

Hun Sen made his remarks at the first national forum to promote understanding of climate change in Cambodia, ahead of a key global summit on the issue this December in Copenhagen, Denmark.

He said it was difficult to expect a deal at the UN climate conference because countries disagreed on many points.

"But we hope that all countries will agree on some common points regarding the obligation of reducing greenhouse gas emissions," he said.

The December 7-18 UN climate summit in the Danish capital will see nations attempt to hammer out a new global climate treaty to replace the Kyoto Protocol, which expires in 2012.