(Recasts, updates with dispute over climate reports)

By Alister Doyle, Environment Correspondent

BONN, Germany, May 7 (Reuters) - The United Nations urged far tougher action to fight global warming on Monday at a 166-nation conference split over how far to trumpet bleak U.N. climate reports that outline rising risks.

"Deep emissions cuts by industrialised countries are needed," Yvo de Boer, head of the U.N. Climate Change Secretariat, told 1,000 government officials at the start of the May 7-18 talks in a Bonn hotel about how to slow warming.

De Boer also said poorer nations should get more involved in fighting climate change, especially big emitters, and that developing nations should get incentives to take part.

Negotiators will try to break gridlock in talks on widening action to brake global warming beyond the end of the first period of the U.N.'s Kyoto Protocol in 2012 amid growing public concern about climate change.

But delegates split over how far to publicise U.N. studies this year that clearly blame human activities, led by burning fossil fuels, for stoking global warming and outline threats including more heatwaves, storms, droughts and rising seas.

The United States and China, the two top emitters of greenhouse gases, opposed a U.N. proposal on Monday to present the reports at the start of a next annual meeting of the world's environment ministers in Bali, Indonesia, in December.

PRESSURE

Diplomats said the U.N. proposal was aimed at upping pressure for action. "Countries opposed to doing much on global warming don't want the reports at Bali because it would highlight how little they're doing," one European diplomat said.

"I objected for procedural reasons," said Osita Anaedu of OPEC-member Nigeria, whose country was among a handful opposed.

Anaedu told Reuters that ministers did not need to deal with the reports, already adopted by governments and drawing on the work of 2,500 scientists. He denied that nations opposed to a presentation in Bali wanted to play down the findings.

A decision would be reached next week.

The third report by the Intergovernmental Panel on Climate Change (IPCC), issued in Bangkok on Friday, said fighting global warming would not undermine the world economy.

The most stringent scenario would cut global economic growth by up to 3 per cent in 2030 -- or less than 0.12 percent a year until then -- and less stringent curbs on emissions of greenhouse gases might even slightly boost the world economy.

Neither the United States nor China have goals under Kyoto, the U.N. plan by 35 industrial nations to cut emissions by 5 percent below 1990 levels by 2008-12.

"The international community should urgently embark on a transition to low carbon societies," The European Union, a main backer of Kyoto, said in a statement at the start of the talks.

The EU said that the IPCC reports meant the world would have to cut emissions of greenhouse gases by 50 percent below 1990 levels by 2050 to limit global warming to a 2 Celsius (3.6 Fahrenheit) rise over pre-industrial times.

Beyond that, the EU fears "dangerous" and possibly irreversible changes to nature. Many nations want to launch formal 2-year negotiations at Bali to agree ways to widen the U.N.'s Kyoto Protocol beyond 2012.

President George W. Bush opposes Kyoto-style caps on emissions, reckoning they will cost U.S. jobs and that Kyoto wrongly omits developing nations until 2012. He prefers big investments in technologies, such as hydrogen or biofuels.

AlertNet news is provided by