COPENHAGEN  Negotiators have all but completed a sweeping deal that would compensate countries for preserving forests, and in some cases, other natural landscapes like peat soils, swamps and fields that play a crucial role in curbing climate change.

Environmental groups have long advocated such a compensation program because forests are efficient absorbers of carbon dioxide, the primary heat-trapping gas linked to global warming. Rain forest destruction, which releases the carbon dioxide stored in trees, is estimated to account for 20 percent of greenhouse gas emissions globally.

The agreement for the program, if signed as expected, may turn out to be the most significant achievement to come out of the Copenhagen climate talks, providing a system through which countries can be paid for conserving disappearing natural assets based on their contribution to reducing emissions.

A final draft of the agreement for the compensation program, called Reducing Emissions From Deforestation and Forest Degradation, or REDD, is to be given on Wednesday to ministers of the nearly 200 countries represented here to hammer out a framework for a global climate treaty. Negotiators and other participants said that though some details remained to be worked out, all major points of disagreement  how to address the rights of indigenous people living on forest land and what is defined as forest, for example  had been resolved through compromise.