The three-day talks, which bring together countries responsible for more than 40 percent of the world's carbon gas emissions, will shine the spotlight on the new US leadership ahead of a forum of 17 major economies in Washington next week.

Kicking off on Earth Day, the talks in Sicily will be a milestone on the way to a UN meeting in Copenhagen in December aimed at sealing an international pact for curbing greenhouse gases beyond 2012.

The G8 club of wealthy nations will be joined by the environment ministers of China, India, Brazil, Mexico, Indonesia, South Africa, South Korea and Egypt.

The United Nations' top climate change official, Yvo de Boer, is attending, along with delegations from the Czech Republic -- holder of the rotating European Union presidency -- plus the European Commission and Denmark as the host of the Copenhagen Conference.

De Boer's office warned that 2009 is a "crunch year in the international climate change negotiations, and it is critical that the G8 countries again show political resolve to tackle climate change."

Scientists have warned that global warming caused by burning fossil fuels on a massive scale could devastate the planet, hitting the poorest countries hardest with floods, droughts and disease.

But the United States, the world's largest emitter of greenhouse gases, never ratified the Kyoto Treaty, which expires in 2012 and is to be replaced by the Copenhagen deal.

The previous administration of former president George W. Bush walked away from the treaty, maintaining that it would prove too costly for American businesses to implement and demanding that developing countries should do more.

US President Barack Obama has made the battle against global warming one of the top priorities of his administration, vowing during a tour of Europe earlier this month that the "US is now ready to lead" on climate change.

The UN goal is either to halve emissions compared with a benchmark year, or to peg temperature increases below 2.0 degrees Celsius (3.6 degrees Fahrenheit) compared to pre-industrial times, according to a UN text unveiled last month.

But deep disagreement remains on how to divvy up the burden between rich and emerging economies and what stepping-stone targets should be set along the way.

Industrialized nations are prepared to take on the larger burden, but want China, India, Brazil and other major carbon polluters also to make commitments of some kind.

The Sicily talks will be a "thoroughgoing debate" with the aim of laying "the basis for a less polluting and more efficent use of engergy in the pursuit of development and well-being for peoples and nations," said Italian Environment Minister Stefania Prestigiacomo.

The talks will "send a powerful political message on biodiversity and the relationship between health and the environment, in particular for children, and ... facilitate dialogue on the issue of climate change," she said in a statement.

The G8 groups Britain, Canada, France, Germany, Italy, Japan, Russia and the United States.