Mitsubishi Heavy Industries said Monday it was studying "various possibilities" for a joint deal with Siemens to buy pieces of French power-generation giant Alstom, with an offer deadline set to expire later in the day.
The Japanese firm and its German partner last week announced they would decide whether to make a formal proposal by June 16, a move that could scupper General Electric's $17 billion bid for Alstom's energy business, which has run into political opposition in France.
"We are considering various possibilities about a proposal concerning some operations of France's Alstom but no decision has been made at the moment," Mitsubishi said in a statement on Monday.
The fast-approaching deadline comes after Japan's leading Nikkei business daily reported last week that Mitsubishi would offer to buy a 10 percent stake in Alstom, as it looks to convince the French government to give it the nod over General Electric.
The Nikkei said the Japanese-German alliance would also buy Alstom's gas and steam turbines businesses for nearly $10 billion.
A source told AFP on Thursday that the minority stake idea was meant to reassure Paris that Mitsubishi wants to forge a broader alliance with Alstom, amid concerns about breaking up the French "national jewel".
In Germany on Monday, the daily Frankfurter Allgemeine Zeitung said that Siemens had come back with a weakened offer for part of Alstom's power-generation business. 
The German industrial group now wants to pay 4.0 billion euros ($5.4 billion) for Alstom's gas turbine activities and will not hand over its rail transportation division as part payment, at least not right away, the German paper said. 
If verified, that offer would be significantly less than the preliminary offer Siemens was said to have put on the table in April: a bid of 10.5 billion to 11 billion euros for Alstom's energy unit, with its train division in the mix.
The French government sees Alstom as a firm of national strategic importance and is concerned about safeguarding jobs at the company -- one of France's biggest private sector employers, with about 18,000 staff nationwide -- as it battles record unemployment and declining industrial competitiveness.
France is worried that Alstom's business base may weaken should its energy assets be bought by foreign firms