An energy plant capable of achieving temperatures of more than 100 million degrees Celsius - the heat of the Sun - could provide the answer to the Earth's dwindling fuel reserves.

It reads like a science fiction, but yesterday a landmark international treaty launched a pounds 7 billion nuclear fusion energy research project to achieve exactly this goal.

The European Commission, representing the 25 EU countries, described the move as an unprecedented attempt to reproduce the physical reaction that occurs in the Sun and the stars. The long- term experiment, which could last for 35 years, is known as ITER - International Thermonuclear Experimental Reactor. It is an attempt to find a large-scale emission-free energy source from readily- available fuels.

European Commission president Jose Manuel Bar-roso was at the signing at the Elysee Palace in Paris, alongside representatives of the six other project partners - the US, India, Japan, Russia, China and South Korea.

The work will be done at Cadarache in France, ultimately building a nuclear fusion reactor to develop an alternative energy source.

"The ITER project is an international collaborative research project on an unprecedented scale which will reproduce the physical reaction - fusion that occurs in the Sun and stars," said a Commission statement.

"Existing experiments have already shown that it is possible to replicate this process on Earth.

Yesterday's signing ceremony marks the end of years of discussions on the practical realities of building a nuclear fusion plant capable of achieving temperatures of more than 100 million degrees Celsius - temperatures necessary to replicate the source of the Sun's energy.

Building work will begin next year.