NUSA DUA, Indonesia - Bali talks headed for a compromise on Saturday to launch negotiations on a global pact to fight climate change after the European Union toned down a key demand for sharp cuts in greenhouse gas emissions by 2020.

The Dec 3-14 talks had been bogged down by a row between the United States, which opposes a reference to non-binding goals for rich countries to curb emissions by 25-40 percent by 2020, and the European Union, which wanted a clear numerical target.

"This is a compromise. We can live with this. It's in a footnote," German Environment Minister Sigmar Gabriel said, referring to the 25 to 40 percent range for cuts.

The United States, the world's top emitter of greenhouse gases, also said it was satisfied.

"We can live with the preamble," U.S. negotiator Harlan Watson told Reuters of the introductory text of the talks draft that had been one of the main source of controversy for Washington because of its inclusion of a target range.

The draft deal could lead the way to agreement at the talks to begin two years of negotiations on a new pact to succeed the U.N.'s Kyoto Protocol, which binds all industrialised nations except the United States to cap emissions of greenhouse gases.

In a sign of the tension at the talks, which have already gone past their Friday deadline, U.N. Secretary-General Ban Ki-moon will make an unscheduled return to the conference on Saturday morning.

A high-level ministerial meeting tasked with negotiating the latest draft ended discussions early on Saturday. The latest draft will be put to a plenary session of all 189 nations in Bali. The session due to resume at midnight.

SCIENCE

Gabriel said that the preamble would include a reference to findings by the Intergovernmental Panel on Climate Change, which said that emissions by rich nations would have to be cut by 25 to 40 percent by 2020 to avert the worst effects of warming.

The U.N.'s IPCC this year said global warming was unequivocal and laid out several emissions reductions targets, some stricter than others, to fight rising temperatures that could bring more floods, heatwaves, spread disease and raise sea levels.

Developing nations said they would resist "pressure and even threats" from some rich countries to step up the fight against climate change.

The main negotiating bloc of developing countries, called the G77, said they were not ready to make new efforts to fight climate change by cutting emissions from fossil fuels. They fear curbs would cramp economic growth aimed at lifting millions out of poverty.

"People are negotiating, they are posturing, and not rising above entrenched national positions," said Angus Friday, Grenada's Ambassador to the U.N. and chair of the Alliance of Small Island states.

"We are just very disappointed at this stage. We are ending up with something so watered down there was no need for 12,000 people to gather here in Bali to have a watered down text, we could have done that by email."