UPDATE 1-CEZ asks for impact study for new nuclear units

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PRAGUE, July 11 (Reuters) - Czech power firm CEZ (CEZPsp.PR: Quote, Profile, Research, Stock Buzz) asked the Environment Ministry for an environmental impact study of the potential construction of two extra units at its Temelin nuclear power plant, the company said on Friday.

The central European country's government has pledged not to approve construction of new nuclear power stations before its term ends in 2010, but has said CEZ could go ahead with the assessment.

CEZ, the largest central European company with market capitalisation of $53 billion, has said the study would take about two and a half years.

The assessment must precede any decision on building the plant.

The Czech Republic is one of Europe's few electricity exporters but dwindling coal reserves, rising demand and ageing fleet of power plants are expected to swing the balance in about 2015.

Nuclear energy has been gaining popularity as energy prices soar and European countries try to replace sources emitting carbon dioxide, blamed for global warming, with cleaner energy.

"No other emissions-free source is capable of producing sufficient amount of electricity," CEZ said in a statement.

"We consider nuclear energy to be the best possible solution from the point of view of economics and the ecology."