Selling the entire Florange facility "would jeopardise the viability of ArcelorMittal's other activities in France, where the group employs 20,000 people," the company said in a statement.

French authorities have told ArcelorMittal it should look to sell the entire plant at Florange and not just the blast furnaces it shut down in October after months of idleness.

The company's warning got a sharp response from Labour Minister Michel Sapin.

"I don't think one has the right to use every weapon, but everyone chooses their own weapons."

What the government wanted, Sapin said, was to create a situation in which a company could take over running the furnaces.

"This company (ArcelorMittal) has to make an extra effort," he added. "We cannot accept the way Mittal wants to get rid of a part of the operation that is fundamental."

ArcelorMittal has given until the end of November for interested buyers of the furnace operations to come forward. But Industrial Renewal Minister Arnaud Montebourg this week suggested the government might take temporary control of the site.

The fate of the site has become a litmus test of Socialist President Francois Hollande's strategy for fighting rising unemployment and raising the flagging competitiveness of French industry.

It is based in the Lorraine region of eastern France, the traditional centre of France's steel industry.