By David Fogarty

SINGAPORE - U.S. President Barack Obama backed on Sunday a compromise proposal to ensure U.N. climate talks next month in Copenhagen don't end in failure.

The decision comes as 19 Asia-Pacific leaders meeting in Singapore said on Sunday it was unlikely a tougher, and legally binding, U.N. climate deal would be agreed at the Dec 7-18 Danish talks.

Bickering over emissions reduction targets, climate financing for poorer nations and how to measure, report and prove emissions reduction steps have bogged down U.N. climate talks for months.

The U.N. has set a December deadline to agree a broader climate pact to replace the Kyoto Protocol from 2013, with that goal now pushed into 2010 at least.

The Danish proposal tries to deal with the reality of too many unresolved issues and the need to deliver a politically binding agreement that would capture progress already achieved in the U.N. negotiations, and at the same time provide for immediate action already from next year.

Support for Danish Prime Minister's Lars Lokke Rasmussen's "one agreement - two purposes" proposal gives the troubled U.N. climate negotiations breathing space by aiming for a politically binding agreement in Copenhagen. Legally binding details would be worked out later.

In particular, it will give Obama's administration more time to try to get a sweeping climate bill through the Senate. Analysts say it needs to pass the Senate in the first few months of 2010 to avoid becoming pushed aside in the run-up to mid-term elections.

But it will not ease the pressure on the United States, the world's number two greenhouse gas emitter, to offer a much tougher mid-term emissions reduction target. The current Senate draft climate bill outlines a reduction of 20 percent below 2005 levels by 2020, but this is far below the cuts the U.N. climate panel says are need from rich countries to avert dangerous climate change.

Many developing countries say rich nations' collective cuts are far below the 25-40 percent reductions from 1990 levels by 2020, the U.N. climate panel says.

The U.N. talks process has run out of time, with too much to be agreed to seal a broad, legally binding agreement in little more than a month.

Hence Denmark's "Plan B", which aims to capitalise on the stated desire of world leaders for Copenhagen to deliver a successful outcome.

Denmark also hopes the agreement would mandate continued legal negotiations and set a deadline for their conclusion.

But analysts point to the risk of that deadline slipping if the U.S. political will to agree on emissions targets and carbon cap-and-trade fails, particularly if the U.S. economy falters.

It also risks growing frustration from developing countries which accuse rich nations of not doing enough to fight climate or help poorer states adapt to its impacts.

Developing nations, including big emitters Indonesia and Brazil, have recently laid out tough, voluntary targets to curb emissions by 2020.

South Korea has opted for a tough voluntary 2020 target as well, underscoring the point that developing nations are already moving to curb their emissions, with some of targets they have announced being more ambitious than those of many rich nations.

All this adds pressure on Denmark to ensure the face-saving proposal yields an agreement in Copenhagen that doesn't erode nations' desire to reach a tougher pact as soon as possible.

It will also need to spell out more clearly how the fight against climate change fairly splits the burden and the financial bill between all nations.