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NUSA DUA, Indonesia, Dec 8 (Reuters) - All nations must do more to fight climate change, with deep cuts in greenhouse gases by rich nations to avoid the worst impacts, a draft proposal at U.N. talks said on Saturday.

The four-page draft, written by delegates from Indonesia, Australia and South Africa as an unofficial guide for delegates at the Dec. 3-14 190-nation talks, said developing nations should at least brake rising emissions as part of a new pact.

It said there was "unequivocal scientific evidence" that "preventing the worst impacts of climate change will require (developed nations) to reduce emissions in a range of 25-40 percent below 1990 levels by 2020."

The draft is the first outline of how to launch talks on a new global deal to replace the Kyoto Protocol, which binds 36 developed nations to cut emissions of greenhouse gases by 5 percent below 1990 levels by 2008-12.

"Current efforts...will not deliver the required emissions reductions," according to the text, obtained by Reuters, that lays out a roadmap to averting ever more droughts, floods, heatwaves and rising seas.

"The challenge of climate change calls for effective participation by all countries," it said. The United States is outside the Kyoto pact and developing nations led by China and India have no 2012 goals for limiting emissions.

And it said global emissions of greenhouse gases would have to "peak in the next 10 to 15 years and be reduced to very low levels, well below half of levels in 2000 by 2050."

It lays out three options for a "roadmap" of what should happen after Bali -- ranging from non-binding talks over the next two years to a deadline for adopting a new global pact at a U.N. meeting in Copenhagen in late 2009.

For rich nations, it says that they should consider ways to step up efforts to curb emissions of greenhouse gase by setting "quantified national emission objectives".

And poor countries should take "national mitigation actions...that limit the growth of, or reduce, emissions," it says. It adds that "social development and poverty eradication are the first and overriding priorities" for poor nations.

Delegates will report back on Monday with reactions to the text.

-- For Reuters latest environment blogs click on: http://blogs.reuters.com/environment/

(Reporting by Gerard Wynn and Alister Doyle, Reuters messaging: ((alister.doyle@reuters.com; +47 900 87 663; Reuters Messaging: rm://alister.doyle.reuters.com@reuters.net))

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