"With old friends and former foes, we will work tirelessly to lessen the nuclear threat, and roll back the specter of a warming planet," Obama said, vowing to pioneer a green revolution in renewable energy.

Obama's remarks marked a stark departure from the stance of his predecessor, George W. Bush, whose rejection of the landmark 2001 Kyoto Protocol almost destroyed multilateral efforts to roll back global warming.

It was only after a firestorm of criticism for holding up the deal that the Bush team signed the "Bali Roadmap" last December during a UN Framework Convention on Climate Change (UNFCCC) meeting that set a two-year deadline for a global agreement.

"We will restore science to its rightful place, and wield technology's wonders to raise health care's quality and lower its cost," Obama said.

"We will harness the sun and the winds and the soil to fuel our cars and run our factories. And we will transform our schools and colleges and universities to meet the demands of a new age. All this we can do. And all this we will do."

Obama has called for an effort to overhaul US energy policy on the scale of the Apollo project that first landed a man on the Moon.

His plan includes unleashing 150 billion dollars over 10 years to create five million new "green" jobs, an 80-percent reduction of greenhouse gas emissions by 2050 and ensuring that 10 percent of US energy consumed comes from renewable sources by 2012 and 25 percent by 2025.

Environmentalists hope Obama will roll back Bush's heritage, moving the United States out of the sidelines in the global arena.

But analysts warn against over-expectations. Obama's room to maneuver may be limited, cramped on one side by the US recession and on the other by the scant time before the December 2009 deadline for completing the new UN climate treaty.

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