The group, which has been hurt by a downturn in the global shipping industry since the financial crisis, is also mulling the sale of shipyards in Finland and China.

Unions are calling for the state, which holds a 33 percent stake in the Saint-Nazaire shipyard to nationalise the site, which employs 2,000 people and is one of the largest in Europe.

"The Saint-Nazaire shipyard needs more orders, not a new shareholder, because the working tool works well," French Industry Minister Arnaud Montebourg said in an interview with the daily, Le Monde, along with three trade unionists.

"Nationalising without any orders would serve no purpose," the minister said. "We met the conditions in December 2012 to land an order for a giant liner and we continue to work to ensure the long-term future of the site."

The government helped the shipyard, then threatened with bankruptcy due to a lack of orders, win a 1 billion euro (841 million pounds) contract to build the world's largest cruise liner.

Five months later, the government is on the front line to ensure a future for the site, which built famous cruise liners such as the Queen Mary 2 commissioned in the early 2000s to sail between Europe and the United Sates.

In March, luxury cruise liner MSC Preziosa, ordered by Italian group MSC, started sailing on the Mediterranean and talks are ongoing between STX and MSC Croisieres for another cruise liner order.

The Saint-Nazaire shipyard will also start building in September another cruise ship for Royal Caribbean Cruise Line to be delivered in 2016.

(Reporting By Muriel Boselli; editing by James Jukwey)