By David Fogarty, Climate Change Correspondent, Asia

SINGAPORE - Asia Pacific leaders are backing away from a target of halving greenhouse gas emissions by 2050, pledging instead to "substantially" slash them by that date, the latest draft of their summit statement says.

The Asia Pacific Economic Cooperation meetings in Singapore is the last major gathering of global decision-makers before a U.N. climate summit in Copenhagen in three weeks meant to ramp up efforts to fight climate change.

But hopes have been dashed that the Copenhagen meeting will yield a legally binding framework for a new deal . Arguments over targets have been a key stumbling block in U.N. negotiations and at other forums, such as the G8.

While the APEC talks are not part of the troubled U.N. climate negotiations, any future emissions goals the 21 members adopt is crucial because the group is responsible for about 60 per cent of mankind's greenhouse gas pollution.

"The clock is ticking to Copenhagen," Australia's Prime Minister Kevin Rudd told an APEC business meeting. "But when you have gathered in Singapore economies which represent a large part of any final negotiated outcome for Copenhagen this is an opportunity we cannot afford to miss."

APEC member China, the world's largest carbon emitter, says it won't take on binding emissions reduction targets until rich nations commit to tough reductions from 1990 levels by 2020.

On Saturday, APEC member South Korea gave the U.N. climate talks a small boost by opting for the toughest of three voluntary emission targets, choosing minus four percent from 2005 levels by 2020, a government source told Reuters in Singapore

Newly industrialized South Korea is not bound by the U.N.'s Kyoto Protocol to take on firm targets, but is under pressure to rein in the rapid growth of it carbon pollution.

The United States and Japan agreed on Friday they would aim to reduce their own greenhouse gas emissions by 80 percent by 2050 and back a global goal to halve emissions by mid-century.

Both are also APEC members and new Japanese Prime Minister Yukio Hatoyama has vowed to cut Japan's emissions by 25 percent from 1990 levels by 2020 -- if other major emitters such as China sign up to an ambitious U.N. deal to fight climate change.

PEAKING EMISSIONS

The initial APEC draft leader's statement said "global emissions will need to ... be reduced to 50 per cent below 1990 levels by 2050."

The latest draft says: "We believe that global emissions will need to peak over the next few years, and be substantially reduced by 2050, recognizing that the timeframe for peaking will be longer in developing economies."

In July, the G8 failed to get major developing nations China and India to sign up to the goal of halving world greenhouse gas emissions by 2050.

Conservation group WWF said this week it was doubtful the minus-50 percent goal would be in the final APEC declaration.

"Normally it doesn't survive in these kinds of circumstances," said Kim Carstensen, head of WWF's global climate initiative.

He was referring to past objections from China and other big developing nations on adopting a 2050 emissions target unless rich nations adopt a 2020 target as well.

Developing countries blame rich nations for most of mankind's greenhouse gas pollution to date and say they should make major reductions first.

The APEC draft doesn't mention a 2020 target but does retain a goal of limiting the global average temperature increase to within 2 degrees Celsius.