Nations must provide power for the 1.6 billion people who live without electricity and wean themselves off energy sources that stoke global warming and geopolitical conflict, the scientists demanded.

"Making the transition to a sustainable energy future is one of the central challenges humankind faces in this century," they said.

Their report, "Lighting the Way: Toward A Sustainable Energy Future," is published by the InterAcademy Council, whose 15 members include the national science academies of the United States, Britain, France, Germany, Brazil, China and India.

It was authored by a 15-member panel whose co-chaired was 1997 Nobel Physics laureate Steven Chu of the United States.

"Overwhelming scientific evidence shows that current energy trends are unsustainable," the report said bluntly.

Its authors sounded a special alarm over the surge in the building of conventional coal-fired power plants in China and other developing countries, as such infrastructure will doubtless be entrenched for decades to come.

"The substantial expansion of coal capacity that is now under way around the world may pose the single greatest challenge to future efforts aimed at stabilising carbon dioxide (CO2) levels in the atmosphere," the report warned.

Managing the greenhouse-gas "footprint" of these plants while encouraging a conversion to carbon capture and storage (CCS) will be a mighty technological and economic challenge, it said.

CCS means piping off CO2 at a plant and then pumping it into geological chambers deep underground, such as disused oilfields, rather than releasing it into the atmosphere.

Many scientists view this pilot technology warily, waiting to be convinced that CCS is safe, for a chamber breach could have potentially catastrophic consequences for the climate system.

The report also appealed for a planet-wide drive in favour of energy efficiency to reduce carbon emissions.

And it spoke loudly in favour of renewable energy, describing its potential as "untapped" and offering "immense opportunities" for poor countries that are rich in sunlight and wind but poor in cash to buy oil and gas.

Nuclear power, as a low-carbon resource, "can continue to make a significant contribution to the world's energy portfolio in the future, but only if major concerns related to capital cost, safety and weapons proliferation are addressed," it cautioned.

Turning to biofuels, the scientist said that these sources hold "great promise", but only through a switch to second-generation sources.

At present, feedstocks such as sugar cane and corn are the main source for biofuels, which is having an effect on global food prices. A more promising, but as yet uncommercialised, goal is using lignocellulose stocks from timber chips and agricultural residues, which microbes digest into fuel.

Other dawning technologies, such as plug-in hybrid cars and hydrogen fuel cells for energy storage, can make an important niche contribution, the scientists said.

But they cautioned that the move to sustainable energy could only happen if nations work together to free up the necessary financial resources and expertise -- and setting a price for carbon to punish pollution and waste and reward clean energy was a key part of the mix.

A 2006 report by the International Energy Agency (IEA) suggested world oil consumption would rise by nearly 40 percent by 2030 as compared with 2005 levels, and CO2 emissions would increase by 50 percent over 2004 levels, under a "business-as-usual" scenario.