UPDATE 2-France still plans to build 60th nuclear reactor

* Many energy experts say reactor is unnecessary

* Sarkozy says Penly key to export French nuclear know-how

* Socialists say will shut 24 out of 59 reactors by 2025 if elected (Adds reaction from green groups)

By Muriel Boselli

PARIS, Nov 25 (Reuters) - France will go ahead with a controversial project to build a 60th next-generation nuclear reactor, President Nicolas Sarkozy said on Friday, as he stepped into a heated pre-election debate over France's dependence on atomic power.

During a visit to Pierrelatte near the Tricastin nuclear power plant in southern France, the French president said the pre-electoral pact by the Socialists and Greens parties to shut 24 reactors across France by 2025 was a threat to the country's industry and the purchasing power of French households.

He reiterated his right-leaning ruling UMP party's will to power ahead with its nuclear programme and said the proposal to shut down more than a third of the country's reactors would cost French consumers 5 billion euros ($6.63 billion) a year.

While the Fukushima catastrophe in Japan in March has fuelled speculation France would give up its plans to build the Penly reactor, in northwestern France, the government has repeatedly denied the project has been ditched.

"We maintain the project to build a reactor in Penly," Sarkozy, who has yet to make his candidacy official for the 2012 presidential election, said on Friday.