The world's biggest steelmaker said last week it was withdrawing from a 2018 deal to acquire Ilva's site in the southern city of Taranto, blaming its decision on a government move to scrap immunity from prosecution over environmental damage in the area.
But Rome said the Amsterdam-listed steelmaker had no legal grounds to withdraw from the contract and accused the company of using the immunity issue as a pretext to walk away.
"Only if Mittal changed his mind and told us that he would respect the commitments envisaged in the contract could (the government) consider a new form of legal shield," Conte said in an interview with newspaper Il Fatto Quotidiano, referring to CEO Lakshmi Mittal.
He added, however, that the company had told him in a previous meeting that the problem was "industrial, and not judicial" and that the group would have u-turned on the investment anyway.
Conte said he would soon meet ArcelorMittal again over the future of the Ilva plant and that his government had already filed an urgent court appeal against their decision.
With the future of the Ilva steelworks in the balance, unions in Taranto staged a one-day strike on Friday to protest over the crisis.
Conte, who met with angry locals, said his government was setting up a task force to approve projects to "relaunch Taranto economically, socially, environmentally and culturally."
He added that Rome was convinced that its legal battle against ArcelorMittal had "great chances of success."
(Reporting by Giulia Segreti; editing by Himani Sarkar and Jason Neely)