But the issue has divided the nearly 200 nations attending the World Summit on Sustainable Development, with some countries resisting calls for a global target for increasing the earth's use of renewables.

The European Union wants the world to aim to get 15 percent of the earth's energy from renewables by 2010. The United States and others are opposed to any target.

But green groups criticised the EU's target, saying that without defining "renewables", it would encourage the building of large environmentally damaging hyrdro dams and do nothing to reduce poor countries' reliance on firewood and dung for energy.

"What does this target mean? Absolutely nothing," said Jennifer Morgan of WWF, formerly the World Wildlife Fund.

Morgan said that renewables, including large hydro and firewood, already account for 14 percent of world energy. Excluding these two, that figure falls to little more than two percent, she said.

The WWF would rather see the summit agree a lower target - 10 percent - but with those two energy sources excluded. That would mean a major boost for solar, wind, geothermal and some types of plant energy.

"This would be a strong step to both providing clean energy services in developing countries and curbing global warming," Morgan said.

Brazil has proposed such a target to be reached by 2012. Delegates said "serious horse-trading" would start on the proposals yesterday.

REDUCING BURDEN ON THE POOR

The squabble touches at the heart of the summit: dragging billions of people out of acute poverty without destroying the environment along the way.

A third of the world's population has no access to modern energy services, leaving them to burn firewood and dung for heat.

Development agencies say this is a major burden for women and children who usually have to collect the fuel and that burning wood threatens forests and causes illness.

Both the United States and the EU defended their positions.

"The EU is trying to combine a degree of ambition with a degree of realism," EU spokesman Michael Curtis said. The EU has set itself a target of doubling the share of renewables within the 15-country bloc to 12 percent from six by 2010.

A United States official said Washington was focused on promoting technologies to reduce pollution from fossil fuels, which are expected to remain the world's dominant energy source in the coming decades.

That opinion is shared by major oil producing countries in the developing world.

Rilwanu Lukman, a delegate for Nigeria which holds the presidency of oil cartel OPEC said: "If you can make fossil fuels cleaner, than you can take away from the argument for renewables. Even coal can be cleaner."

The final wording will be included in a broad action plan for sustainable development that world leaders are due to sign up to next week. (Additional reporting by Matt Daily).