Shares in utility group Suez have risen after billionaire French investor Francois Pinault refused to rule out a possible takeover bid for the firm.
The government supports Gaz de France's merger plan with Suez
Mr Pinault's holding company Artemis said it had taken no decision yet about making a bid for the French water firm, but added: "All options remain open."
Reports last week suggested that Mr Pinault planned to put forward a 70bn-euro ($92bn; £47bn) bid for Suez.
Such a move could scupper a planned merger between Suez and Gaz de France.
Shares in Suez rose 1.4% in morning trading on the Paris stock exchange.
France's Capital magazine said Mr Pinault intended to break up Suez if he succeeded with his bid, selling the firm's energy assets to state-run Gaz de France and its environmental operations to French utility group Veolia.
Government-backed plans for an 80bn-euro merger between Suez and Gaz de France have faced stiff political opposition in France, because the deal would in effect require the privatisation of Gaz de France.
The proposed merger of the two companies to create a French national champion followed reports that Italian group Enel was planning to make a bid for Suez.
A court has since ruled that the French deal cannot go ahead until the full liberalisation of European Union energy markets on 1 July - after France's presidential election.
Mr Pinault's business empire includes luxury group PPR, which owns the Gucci fashion label.