German deputy environment minister Matthias Machnig said solar systems behind the plan had "enormous potential" and that Germany had developed some of the field's leading technology.

The Desertec Industrial Initiative (DII) is powered by 12 mostly German companies from engineering, energy and finance sectors but has also won support from groups in Algeria and Spain and from officials in Egypt and Jordan.

The project, scheduled for completion in 2050, would see solar power generators span North Africa and the Middle East to Saudi Arabia, with the electricity generated shared by producer countries and European partners.

The technique, called solar thermal electrical generation (STEG), uses reflected sun rays to create intense heat and steam that drives a generator.

Water desalinisation plants for host nations were another key part of the plan.

The environmental group Greenpeace's spokesman Andree Boehling said: "We support and welcome this initiative" and forecast that "around a quarter of global electricity supply could come from solar electricity in deserts."

Matthias Fawer, who covers sustainable energy at the private Swiss bank Sarasin told AFP the initiative was "a visionary concept" but noted it was not the only solution.

"I wouldn't bet on one horse," he said, adding that it was important to also speak about developing wind energy parks in the North Sea and geo-thermal energy in places where that was appropriate.

"It's the combination that is viable and makes renewable energy so strong," Fawer said.

Greenpeace called the Desertec initiative "another building block" for the future but said it was "not an alternative to decentralised technologies like photo voltaic or wind energy."

German Social Democratic deputy Hermann Scheer said 400 billion euros could be invested in a European grid of decentralised alternative energy sources rather than having one key project in the hands of major corporations.

But Fawer said helping North Africa, a major source of European immigrants, develop its economy was not like throwing money out the window.

"We need to support this continent," he stressed. "It's a good deal, Europe and Africa should work much closer together."

Jordan Prince Hassan ibn Talal expressed a similar view when the project was unveiled on Monday.

Partnerships formed as a result of the project "will open a new chapter in relations between the people of the European Union, West Asia and North Africa," he was quoted by a statement as saying.

A study conducted by Desertec, Greenpeace and the Wuppertal environmental research institute concluded the project could create two million jobs, and Desertec spokesman Tim Hufermann told AFP 80 percent of the power generated would stay in producer countries.

The remainder is said to be enough to satisfy 15 percent of Europe's electricity needs.

Critics say few jobs would be created in producer countries however, and the business daily Handelsblatt warned Monday against fostering "eco-colonialism."

The massive project would cover 6,000 square kilometres (2,300 square miles), including 2,500 for power plants and 3,500 for the distribution grid.

"They are already building plants" in Egypt, Spain and Tunisia that could be integrated into the overall network, Hufermann said.

Desertec has estimated the initial start-up cost at 10 billion euros.

Fawer and Greenpeace were both encouraged by the fact that big energy groups like E.ON and RWE of Germany were involved, though some have warned that if too many power companies got on board it might raise competition issues.

But the plan's enthusiastic reception meant "maybe there are new concepts beyond coal and gas and beyond nuclear power that are becoming viable and are also valid on a cost basis," the analyst said.

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