The European Union threatened on Thursday to boycott U.S. talks among top greenhouse gas emitting nations, accusing Washington of blocking goals for fighting climate change at U.N. talks in Bali.

If we would have a failure in Bali it would be meaningless to have a major economies' meeting in the United States, Humberto Rosa, Portugal's Secretary of State for Environment, said on the penultimate day of the two-week talks.

We're not blackmailing, he said, ratcheting up a war of words with Washington at the 190-nation talks. If no Bali, no MEM (major emitters' meeting).

Portugal holds the rotating EU presidency and Rosa is the EU's top negotiator in Bali.

We don't feel that comments like that are very constructive when we are working so hard to find common ground on a way forward, said Kristin Hellmer, a White House spokeswoman in Bali.

The December 3-14 Bali talks are split over the guidelines for starting two years of formal negotiations on a deal to succeed the Kyoto Protocol, a U.N. pact capping greenhouse gas emissions of all industrial nations except the United States until 2012.

Washington, long at odds with many of its Western allies on climate policies, has called a meeting of 17 of the world's top emitters, including China, Russia and India, in Hawaii late next month to discuss long-term cuts.

President George W. Bush intends the Honolulu meeting to be part of a series of talks to feed into the U.N. process. Washington hosted a similar meeting in September, which attracted few top officials and achieved little.

The EU wants Bali's final text to agree a non-binding goal of cuts in emissions of 25 to 40 percent below 1990 levels by 2020 for industrial economies as a roadmap for the talks.

The United States, Japan, Canada and Australia are opposed, saying any figures would prejudge the outcome.

BLOCKING

Those who are suggesting that you can magically find agreement on a metric when you are just starting negotiations, that in itself is a blocking element, said James Connaughton, Chairman of the White House Council on Environmental Quality.

Despite opposition to Kyoto, the United States plans to join a new treaty, meant to be agreed in Copenhagen in late 2009 with participation of developing nations led by China and India.

We will lead, we will continue to lead. But leadership also requires others to fall in line and follow, Connaughton said. U.S. climate policy is to invest heavily in new technologies such as hydrogen and clean coal, without Kyoto-style caps.

Rosa said: Whatever comes out of Bali must rely on science. This link is fundamental and for us that means figures.

The range of 25-40 percent cuts for rich nations was given in studies by the U.N. Climate Panel this year, which blamed mankind for stoking warming and urged quick action to avert ever more floods, droughts, melting glaciers and rising seas.

On the sidelines, climate campaigner and former U.S. Vice President Al Gore, fresh from collecting the Nobel Peace Prize in Oslo with the U.N. Climate Panel, arrived in Bali to give a speech to delegates about the risks of warming.

On other issues, the Bali talks made progress.

They agreed a deal in principle to share technology -- such as wind turbines or solar panels -- meeting a key demand of poor nations who feel the rich have a responsibility to make up for emissions of greenhouse gases since the Industrial Revolution.

I am fairly hopeful, said Yvo de Boer, the U.N.'s top Climate Change official, of the technology deal.

In the past two weeks, the talks have also agreed the workings of a fund to help poor nations adapt to climate change and are near a plan to help slow tropical deforestation.

Kyoto binds 37 industrialized nations to cut emissions by an average of 5 percent below 1990 levels by 2008-12. Poorer nations, led by China and India, are exempt from curbs. Washington pulled out in 2001, saying Kyoto would harm the U.S. economy and wrongly excluded goals for developing countries.

The United Nations says a Kyoto successor has to be in place by 2009 to give governments time to ratify the new deal by the end of 2012 and to give markets clear guidelines on how to make investments in clean energy technology.

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(Additional reporting by Alister Doyle, Adhityani Arga and Emma Graham-Harrison in Bali; editing by David Fogarty.)

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