"A lot of people are afraid of discussing the future," said EU head delegate Pieter van Geel, the Dutch environment secretary.

His deputy, Yvo de Boer, said negotiations were very tense and almost fell apart in a marathon overnight session.

The meeting of nearly 200 nations and 6000 participants started on a high note 12 days ago after Russia's ratification of the Kyoto protocol last month, allowing the treaty to take effect in February with a seven-year delay.

Kyoto will cut emissions in industrialized countries by 5 percent from 1990 levels, a first small step. The EU believes it will have to reduce its emissions by at least half by mid-century and mandatory cuts are the preferred method.

The EU came to Buenos Aires wanting to narrow differences with the United States, the source of 25 percent of the world's heat-trapping gases, and the large developing economies excluded from Kyoto like China and India.

But it soon became clear that Washington was sticking to its 2001 decision to bow out of Kyoto for fear of the impact that mandatory emissions curbs would have on economic growth. Moreover, the delegation reiterated that it would be "premature" to negotiate for after 2012.

The Argentine hosts and the EU found a compromise in the form of a seminar for 2005 for an informal exchange of information rather than talks on a post-Kyoto regime.

Some negotiators said, however, that the seminar will surely touch on the future, and that would be positive for a UN effort that languished in recent years.

Environmental groups said they were frustrated by the results.

"The outcome is certainly disappointing," said Steve Sawyer, climate expert for Greenpeace. "The efforts to move things forward on climate mitigation for reducing gas emissions are very small."

'OPEC PLAYS BIGGER ROLE'

While the United States remained intransigent on future talks, the oil-producing nations and Saudi Arabia in particular also thwarted the EU agenda.

"It would be a big mistake to put this all down to the United States. Not for the first time, the oil-producing countries play a far bigger role than anyone ever gives them credit for," said British Environment Secretary Margaret Beckett.

Negotiators had to overcome OPEC resistance to push through a partial climate aid package for developing countries, the most hurt by the rise in world temperatures linked to man-made emissions like carbon dioxide.

The developing nations also resisted the EU's agenda, aware that many Europeans believe the fast-growing economies should stop their dirty practices, like coal-intensive industry or burning forests to make way for farming.

"We are not prepared to discuss reductions in emissions," said Brazilian head delegate Everton Vieira Vargas.

The next big moves on climate change may come from British Prime Minister Tony Blair, who has made the issue a cornerstone of his country's G8 presidency in 2005. He will be looking to soften up US President George W. Bush on climate and also engage the big developing economies.