(Repeats story published late on Thursday)
By Martin Dokoupil and Jan Korselt
PRAGUE, May 22 (Reuters) - Nuclear energy is a low-carbon source that may help Europe in fighting climate change and raise energy security, the head of the bloc's executive Commission, Jose Manuel Barroso, said on Thursday.
Barroso said nuclear power was one of the cheapest low-carbon power sources, but safety must remain of paramount concern, and it was up to individual member states to decide on their energy mix.
"Nuclear energy can of course make a major contribution to this battle against climate change," Barroso said at the European Nuclear Energy Forum, which opened in Prague on Thursday.
"Nuclear energy also helps to enhance EU's security of energy supplies and it increases diversification of our energy sources and reduces our dependence on imported gas," he said.
Some European Union countries have been turning in favour of building new nuclear power stations to meet growing energy demand and the need to cut carbon dioxide emissions blamed for global warming.
But the EU has avoided giving guidance on the issue, given opposition in some member states, such as the fiercely anti-nuclear Austria.
France, in contrast, uses nuclear power as a source of 78 percent of its electricity. Britain is eyeing expansion beyond its current 19 percent, and a number of former communist new member-states plan to raise their nuclear power generating capacity.
The east European nations are much more dependent on Russian natural gas than the entire EU, which takes a quarter of its gas from Russia, and also face electricity shortages.
Prime Minister Robert Fico of Slovakia, which seeks to complete 2 nuclear units and build another one, said nuclear energy was necessary to meet energy security goals.
"Several years ago, supporters of nuclear energy were looked upon as witches, now we are discussing it with top EU officials," Fico said. "It is absolutely clear that we will not achieve energy security without nuclear energy."
Czech Prime Minister Mirek Topolanek, hosting the forum, said the EU would not meet its emissions goals without nuclear expansion.
The EU aims to cut carbon dioxide emissions to at least 20 percent below 1990 levels by 2020, but by then many of its existing nuclear power stations, which have virtually no emissions, will have closed.
Barroso said there was no clear guidance on nuclear in the carbon dioxide plan.
"Honestly, one cannot say if our 2020 goals include nuclear (energy) ... certainly such ambitious targets for greenhouse gas solutions create a great opportunity for all carbon-free sources including nuclear energy."
At present, 15 out of 27 EU member states produce electricity from nuclear power plants. (Writing by Jan Lopatka; Editing by Ben Tan)