The long-awaited United Nations summit on climate change has got underway in the Danish capital Copenhagen, with delegates from 192 countries attending.Speaking at the opening session, Danish Prime Minister Lars Lokke Rasmussen called on world leaders to show ambition, courage and vision in their decisions.

Any agreement thrashed out over the next 12 days is intended to replace the 1997 Kyoto Protocol. Targets set at Kyoto run out in 2012. World leaders who will attend the talks include US President Barack Obama, Chinese Prime Minister Wen Jiabao, Indian Prime Minister Manmohan Singh, Brazilian President Luiz Inacio Lula da Silva and the heads of EU.

The main goals of the summit are to reach consensus on targets curbing greenhouse gas emissions - in particular by developed countries - and on financial support for mitigation of climate change in developing nations. A carbon trading scheme aimed at ending the destruction of the world's forests by 2030 will also be drawn up.

The role of President Obama is seen as crucial to the success of a pact on climate change. His predecessor George W. Bush did not commit to the objectives laid down in the Kyoto Protocol. In July, the G8 bloc of industrialised nations and some major developing countries adopted a target of keeping the global average temperature rise since pre-industrial times to two degrees Centigrade.

It is expected that further talks will be needed next year to work out the hoped-for accord in Copenhagen.

Protesters in Copenhagen by EPA