A drive to agree a U.N. climate pact in Copenhagen in December risks failure unless world leaders revive bogged-down negotiations at a U.N. summit in New York on September 22, experts say.

Recriminations between rich and poor nations about how to share out curbs on greenhouse gas emissions, and scant aid from recession-hit rich nations, mean the world is far from a deal. A draft treaty is an unmanageable 200 pages long.

Now the onus is on heads of government, Achim Steiner, head of the U.N. Environment Program, told the Reuters Global Climate and Alternative Energy Summit.

He said that a one-day climate summit at U.N. headquarters on September 22 was a chance to show world leaders that there is a high risk that a deal will not emerge from Copenhagen unless they get more involved in spurring the negotiations.

And there is a lot to sort out in the next three months, according to participants in September 8-10 Reuters summit.

Brazil's Environment Minister Carlos Minc said a plan by U.S. President Barack Obama -- struggling to secure healthcare reforms before turning to climate -- to cut U.S. greenhouse emissions back to 1990 levels by 2020 was unacceptably weak.

We don't accept that, it's very poor, he said, adding that the goal should be closer to something beyond a 20 percent reduction. The U.S. 2020 goal is the weakest of any developed nation, but Obama promises a deep 80 percent cut by 2050.

OBAMA HEALTHCARE

Right now we are focused on this crusade for healthcare reform for the country and that's where our time and energy will go for the days ahead, U.S. Interior Secretary Ken Salazar said on Tuesday.

Even so, he told the Reuters summit, We want both (healthcare and climate bills).

Yvo de Boer, head of the U.N. Climate Change Secretariat, said at the summit he had become more upbeat about prospects for a deal in Copenhagen but said that negotiators had to pick up the pace at a next meeting in Bangkok at the end of September.

I'm more confident than I've been before, he said in an interview this week, pointing to what he said were encouraging signs this week such as a plan by Japan's incoming government to deepen planned cuts to 25 percent below 1990 levels by 2020.

He said that the September 22 summit, organized by U.N. Secretary-General Ban Ki-moon, was a unique opportunity to send a signal of global backing for a deal.

And it was also a chance to widen meetings beyond a core group of nations such as China and the United States, which account for about 80 percent of emissions, to outsiders such as small island states or African nations.

There seems to be no shortage of meetings amongst the countries that are causing climate change but a paucity of meetings that involve countries suffering the consequences, he said.

Small island states such as Tuvalu or the Maldives fear rising sea levels could wipe them off the map. U.N. studies suggest up to 250 million people in Africa could suffer extra stress on water supplies by 2020 -- threatening more hunger.

Talks on finance are also deadlocked.

The European Union, which calls itself a leader in climate efforts, on Thursday scaled back its likely aid for developing nations to 2-15 billion euros ($3-$22 billion) a year by 2020 to help them to do more to combat climate change.

Last week, it had indicated it might pay 13-24 billion euros of a total bill of around 100 billion. Leaders of the Group of 20 will meet in Pittsburgh on September 24-25, partly to discuss climate finance.

De Boer said he hoped that Copenhagen would come up with perhaps $10 billion to kickstart actions by developing nations with longer-term needs to be defined later. No nations have yet offered cash to that initial pot, he said.

In the longer term, he said experts have estimated needs at $200 billion a year to curb emissions worldwide and $100 billion a year to help poor nations adapt to changes such as heatwaves, floods or disease.

(With reporting by Raymond Colitt in Brasilia, Richard Cowan in Washington, Pete Harrison in Brussels, Gerard Wynn in London, David Fogarty in Singapore, Mary Milliken in Los Angeles)

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