Top emitters of greenhouse gases tried on Monday to break a deadlock about sharing the burden of cuts in a U.N. climate pact, and Washington rejected charges that it was lagging Europe in fighting global warming.

Environment ministers from 17 nations including the United States, China, Russia, Japan, Germany and France met for the first of two days of U.S.-led talks in Paris hoping to ease splits on emissions cuts, aid to the poor and new technologies.

France told the meeting that a new U.N. climate treaty, expected to be agreed in Copenhagen in December, would bring economic opportunities and would not herald a downturn caused by rising energy costs.

Copenhagen ... is not the start of a recession, it is a new start toward a development that is low in carbon, sustainable, robust and job-creating for all countries of the world, French Environment Minister Jean-Louis Borloo told the opening session.

In the U.N. negotiations, developing nations led by China and India have accused rich nations of worrying about recession and failing to keep promises that they would take the lead in cutting the use of fossil fuels that release greenhouse gases.

Also, U.N. Secretary-General Ban Ki-moon said on Sunday that Washington was lagging the European Union in promises to fight global warming, even though President Barack Obama plans far tougher curbs than his predecessor, George W. Bush.

I don't think it's correct to say that Europe is proposing a lot and the United States little, Todd Stern, U.S. Special Envoy for Climate Change, told Tuesday's edition of the French daily Le Monde.

If you look at things from the point of view of the progress that each nation will have to make to reach its objectives, the U.S. level of effort is probably equal, or superior, to that of Europe, Stern said.

2020 CUTS

A bill approved by a key congressional panel last week would cut U.S. emissions by 17 percent from 2005 levels by 2020 -- to just below 1990 levels after a sharp rise -- and by 83 percent from 1990 levels by 2050.

The European Union has promised to cut emissions more deeply, by 20 percent below 1990 levels by 2020, and by 30 percent if other rich nations follow suit.

The aim of the reductions is to slow global warming, averting more heatwaves, rising sea levels, extinctions, floods and droughts.

Stern said that Europe's cuts were helped by a good policy but also factors such a collapse of east German emissions, closure of coal mines in Britain and slower economic growth than in the United States. Bush rejected any caps on U.S. emissions.

Analysts say the Major Economies Forum (MEF) talks at the French Foreign Ministry, the second of three preparatory meetings before a summit in Italy in July, are a chance to air differences away from the public gaze.

The U.N. negotiations have somewhat fallen back to North-South finger-pointing, said Jake Schmidt of the Natural Resources Defense Council in Washington. The MEF is a crucial place where you can make progress on some of the difficult issues out of the limelight.

The EU cuts fall far short of demands by China and India that Europe cut its emissions by at least 40 percent from 1990 levels by 2020. The U.N. Climate Panel had suggested 2020 cuts by rich nations of 25 to 40 percent below 1990 levels to avoid the worst of climate change.

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(Editing by Tim Pearce)