-- The objective of ITER is to demonstrate the feasibility of producing electricity from a fusion reaction, which involves fusing atomic nuclei at extremely high temperatures inside a giant electromagnetic ring.

It is the same process by which stars, including the sun, produce energy. Deuterium, the major fuel to operate the reactor, will be extracted from seawater.

-- Proponents of the project argue that if it succeeds it will result in potentially inexhaustible and cheap supplies of energy, eventually replacing oil and gas. Opponents say the project is only experimental and it will be at least 50 years before a commercially viable reactor is built. Some also contend that fusion fuel is neither clean nor safe, although it would be a safer energy source than nuclear fission.

-- Participants in the venture include China, the European Union, Japan, South Korea, Russia and the United States. The idea of a nuclear fusion reactor was floated by the then Soviet Union in 1985 as a showpiece for international cooperation during the Cold War.

The United States, a founding member of the ITER, pulled out in 1998 and re-entered in 2003. Canada withdrew in 2003.

-- Construction of the 500 megawatt reactor is forecast to cost about 4.6 billion euros ($6.14 billion) and take 10 years to complete. The reactor is expected to be operational for 20 years. The European Union intends to cover 40 percent of the cost and France will contribute an additional 10 percent.