China, which makes 70 percent of the world's light bulbs, has agreed to phase out incandescent bulbs in favour of more energy-efficient ones, and the transition could be made in the next 10 years, according to Monique Barbut, chief executive officer of the Global Environment Facility.

China's program will be formally announced in December at a meeting of climate negotiators in Bali, Indonesia, she said.

China is the first developing country to agree to join this program, and the facility will invest about US$25 million for the Chinese program alone.

The Global Environment Facility is one of the richest and least-known environmental funding agencies worldwide.

With a current trust fund of about US$3.2 billion, the Washington, DC-based agency is the financial arm for international intergovernmental agreements on biodiversity, climate change and persistent organic pollutants. It also supports agreements on international waters, ozone and desertification.

"An efficient light bulb costs four times more than an inefficient light bulb - it lasts 10 times longer but it's four times more (expensive) - and for many very poor people ... the problem is that they can't afford the four times more at one time," Barbut said.

Compact fluorescent lamps use between a quarter and a fifth of the energy of incandescent bulbs producing the same light.

The matter is being discussed by countries in the European Union and the United States, she said, adding that China is ahead of the United States in this respect.