PORT OF SPAIN: World leaders sought today to spur on the global-warming debate ahead of a Copenhagen climate conference that has been fired up by pledges from China and the United States to cut emissions.

UN chief Ban Ki-moon, French President Nicolas Sarkozy and leaders of 53 Commonwealth nations were to tackle climate change at a summit in Trinidad, 10 days before the global conference starts.

The Commonwealth is seeking a common stance for the talks, said Trinidad and Tobago Prime Minister Patrick Manning who is hosting nations ranging from Britain and India to minnows Lesotho and Tuvalu.

A political statement from the Commonwealth “comes with the weight of so many countries and so many people, that therefore we feel it can have some effect on influencing the way that the discussions go in Denmark,” Manning said.

Climate change and rising sea levels blamed on global warming -- said to be caused by greenhouse gases emitted mostly by the world’s industrial powerhouses -- threaten many developing nations who want their voices heard in Copenhagen.

Fears that the conference starting December 7 would fail to reach a deal were eased this week with pledges by Beijing and Washington.

The offers by the world’s two biggest greenhouse gas emitters were widely hailed, even if there were questions over how effective they would be.

They were “extremely encouraging in making Copenhagen a success”, Sarkozy said in Brazil Thursday at a meeting of Amazon nations to urge the climate talks to preserve the rainforests.

The United States said it was aiming to curb emissions by 17 per cent from 2005 levels by 2020.

It is less than calls by the European Union, Japan and UN scientists -- but the first concrete numbers put on the table by the world’s largest economy and second biggest polluter.

US President Barack Obama will also present at Copenhagen longer-term pledges of a 30 percent reduction in emissions by 2025, 42 per cent by 2030 and 83 per cent by 2050, officials said.

Analysts however warned it was a risky gamble for Obama because the goals were conditional on action in Congress.

“The administration has to walk a very careful balance here,” Michael Levi of the Council on Foreign Relations told AFP.

China said that by 2020, it would cut the amount of carbon dioxide emitted per unit of gross domestic product (GDP) by 40 to 45 per cent compared to 2005 levels.

That is essentially a pledge of greater energy efficiency: with electricity demand soaring, China relies on carbon-belching coal to generate about 70 percent of its energy needs.

China’s Communist Party leadership pledged Friday to “actively” tackle climate change while sticking to its economic expansion.