Options suggested for raising billions of dollars in incentives include markets that would allow trading in the carbon dioxide locked up in trees, higher aid from rich nations and levies on airline tickets or on international shipping.

"For many developing countries, avoiding deforestation is pretty much the only way they can engage in the climate change regime and reap some benefits," said Yvo de Boer, head of the UN Climate Change Secretariat.

A UN climate conference in Bali last year agreed to explore ways to pay people in the developing world to leave forests standing - trees soak up carbon dioxide as they grow and release it when they rot or are burned.

The Accra meeting is working on details as part of a plan to agree a sweeping new UN climate treaty by the end of 2009 to avert heatwaves, droughts, more powerful storms, risks of more disease and rising sea levels.

Brice Lalonde, a representative from France said that the EU was willing to consider extra aid or to work out new forms of carbon trading. The European parliament voted this year to auction 15 percent of emissions from aviation and use proceeds for measures such as slowing deforestation.